Update README.rdoc

The README lacked instructions on how the user name that shows up in the revision
message is generated so I've added a suggested blurb on this.

I've also added a change to the gemfile setting in the README
as was suggested in the issues section to make sure that you
pick up the correct gem.
Merge pull request #33 from gitgary/patch-1

Update README.rdoc
add page to compare path in form, it was always wiki/compare and root page will be compared
fix text area content
don't use attr_protected in rails4
use :data => {:confirm, in rails4 is deprecated
fix deprecation in association for rails4
fix for rails4, use strong parameters, not copy id to version
set rows in textarea, rails4 has no default