Redmine

In #3209 you added support for excalamation marks in url but it disabled the possibility to do linkable image.

Suggested patch:

When we arrive at evaluating this re, the input looks like either like:

<p>!/attachments/download/1!</p> <-- we want to expand 
or 
<p>http://www.pouet.com/ahah!lol! <-- we don't want to expand

But also like, when we have "p=."

<p :redsh#1:>!/attachments/download/1!</p>

Therefore I suggest to use this re in redcloth3.rb :

    IMAGE_RE = /
            (<p>|<p\s:.*:>|\s|^) # start of line?
            \!                   # opening