Kohana 3.3 support

[Tested]
- Users
- Throttle
[Untested]
- Groups
- Permissions
coding style fixes
Added Kohana validation rules to groups

forgot to replace && with AND
redid User::unique_key_exists
Group bug fix

validation rule wasn't defined correctly
fixed group validation bug
serialize permission fields
fixed Group::validate
finally got groups working
added proper delete functionality
DateTime fix
Merge pull request #253 from happyDemon/master

Kohana 3.3 support