Update mysql gem, and set upper limit

Avoiding LoadError:
Please install the mysql adapter: `gem install
activerecord-mysql-adapter` (can't activate mysql (~> 2.8.1), already
activated mysql-2.9.0. Make sure all dependencies are added to Gemfile.)
use activerecord 3.2.6
Patch select_value for MysqlAdapter
Update activerecord to 3.2.11
Merge pull request #172 from sanemat/feature/activerecord

Update gems, fix MysqlAdapter issue