Reverting mysql to 2.1.1

- Unfortunately mysql has changed the way it handles the charset setting such that
it now causes encoding issues on many setups where 'utf8' is apparently not the
correct setting.
- We need to revert this upgrade until the issue is fixed or we have a way to handle
it nicely for our users.
Merge pull request #4475 from ErisDS/revert-mysql

Reverting mysql to 2.1.1
Version bump to 0.5.5
Remove master warning from stable branch