Redmine

Hello, I need to use gruff in my plugin, I have installed it correctly but:
- when I add the line gem "rubygems-update", "~> 2.0.3" in the Gemfile , the two services of redmine (Thin_redmine and Thin_redmine2) will always be stopped.
- when I remove that line, the code will be not valid for redmine:

require 'rubygems'
  require 'gruff'
  g = Gruff::Line.new
    g.title = "My Graph" 
    g.data("Apples", [1, 2, 3, 4, 4, 3])
    g.data("Oranges", [4, 8, 7, 9, 8, 9])
    g.data("Watermelon", [2, 3, 1, 5, 6, 8])
    g.data("Peaches", [9, 9, 10, 8, 7, 9])
    g.labels = {0 => '2003', 2 => '2004', 4 => '2005'}
    g.write('my_fruity_graph.png')

=======>
LoadError (cannot load such file -- gruff):
activesupport (3.2.11) lib/active_support/dependencies.rb:251:in `require'
activesupport (3.2.11) lib/active_support/dependencies.rb:251:in `block in require'
activesupport (3.2.11) lib/active_support/dependencies.rb:236:in `load_dependency'
activesupport (3.2.11) lib/active_support/dependencies.rb:251:in `require'
plugins/relecture/app/controllers/relectures_controller.rb:3:in `<top (required)>'
activesupport (3.2.11) lib/active_support/dependencies.rb:251:in `require'
activesupport (3.2.11) lib/active_support/dependencies.rb:251:in `block in require'
activesupport (3.2.11) lib/active_support/dependencies.rb:236:in `load_dependency'
activesupport (3.2.11) lib/active_support/dependencies.rb:251:in `require'
activesupport (3.2.11) lib/active_support/dependencies.rb:359:in `require_or_load'
activesupport (3.2.11) lib/active_support/dependencies.rb:502:in `load_missing_constant'
activesupport (3.2.11) lib/active_support/dependencies.rb:192:in `block in const_missing'
activesupport (3.2.11) lib/active_support/dependencies.rb:190:in `each'
activesupport (3.2.11) lib/active_support/dependencies.rb:190:in `const_missing'
activesupport (3.2.11) lib/active_support/inflector/methods.rb:230:in `block in constantize'
activesupport (3.2.11) lib/active_support/inflector/methods.rb:229:in `each'
activesupport (3.2.11) lib/active_support/inflector/methods.rb:229:in `constantize'
activesupport (3.2.11) lib/active_support/dependencies.rb:554:in `get'
actionpack (3.2.11) lib/action_dispatch/routing/route_set.rb:69:in `controller_reference'
actionpack (3.2.11) lib/action_dispatch/routing/route_set.rb:54:in `controller'
actionpack (3.2.11) lib/action_dispatch/routing/route_set.rb:32:in `call'
journey (1.0.4) lib/journey/router.rb:68:in `block in call'
journey (1.0.4) lib/journey/router.rb:56:in `each'
journey (1.0.4) lib/journey/router.rb:56:in `call'
actionpack (3.2.11) lib/action_dispatch/routing/route_set.rb:601:in `call'
rack-openid (1.3.1) lib/rack/openid.rb:98:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
rack (1.4.1) lib/rack/etag.rb:23:in `call'
rack (1.4.1) lib/rack/conditionalget.rb:25:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/head.rb:14:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/flash.rb:242:in `call'
rack (1.4.1) lib/rack/session/abstract/id.rb:205:in `context'
rack (1.4.1) lib/rack/session/abstract/id.rb:200:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/cookies.rb:341:in `call'
activerecord (3.2.11) lib/active_record/query_cache.rb:64:in `call'
activerecord (3.2.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:479:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/callbacks.rb:28:in `block in call'
activesupport (3.2.11) lib/active_support/callbacks.rb:405:in `_run__144659805__call__536271176__callbacks'
activesupport (3.2.11) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.11) lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
activesupport (3.2.11) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.11) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
railties (3.2.11) lib/rails/rack/logger.rb:32:in `call_app'
railties (3.2.11) lib/rails/rack/logger.rb:16:in `block in call'
activesupport (3.2.11) lib/active_support/tagged_logging.rb:22:in `tagged'
railties (3.2.11) lib/rails/rack/logger.rb:16:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/request_id.rb:22:in `call'
rack (1.4.1) lib/rack/methodoverride.rb:21:in `call'
rack (1.4.1) lib/rack/runtime.rb:17:in `call'
activesupport (3.2.11) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.4.1) lib/rack/lock.rb:15:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/static.rb:62:in `call'
rack-cache (1.2) lib/rack/cache/context.rb:136:in `forward'
rack-cache (1.2) lib/rack/cache/context.rb:245:in `fetch'
rack-cache (1.2) lib/rack/cache/context.rb:185:in `lookup'
rack-cache (1.2) lib/rack/cache/context.rb:66:in `call!'
rack-cache (1.2) lib/rack/cache/context.rb:51:in `call'
railties (3.2.11) lib/rails/engine.rb:479:in `call'
railties (3.2.11) lib/rails/application.rb:223:in `call'
railties (3.2.11) lib/rails/railtie/configurable.rb:30:in `method_missing'
rack (1.4.1) lib/rack/urlmap.rb:64:in `block in call'
rack (1.4.1) lib/rack/urlmap.rb:49:in `each'
rack (1.4.1) lib/rack/urlmap.rb:49:in `call'
thin (1.3.1) lib/thin/connection.rb:80:in `block in pre_process'
thin (1.3.1) lib/thin/connection.rb:78:in `catch'
thin (1.3.1) lib/thin/connection.rb:78:in `pre_process'
thin (1.3.1) lib/thin/connection.rb:53:in `process'
thin (1.3.1) lib/thin/connection.rb:38:in `receive_data'
eventmachine-1.0.0-x86 (mingw32) lib/eventmachine.rb:187:in `run_machine'
eventmachine-1.0.0-x86 (mingw32) lib/eventmachine.rb:187:in `run'
thin (1.3.1) lib/thin/backends/base.rb:61:in `start'
thin (1.3.1) lib/thin/server.rb:159:in `start'
thin (1.3.1) lib/thin/controllers/controller.rb:86:in `start'
thin (1.3.1) lib/thin/runner.rb:185:in `run_command'
thin (1.3.1) lib/thin/runner.rb:151:in `run!'
thin (1.3.1) bin/thin:6:in `<top (required)>'
bin/thin:16:in `load'
bin/thin:16:in `<main>'