fix for connection pooling.

by defining these methods in the adapter class, we prevent calls from the ConnectionPool class being proxied to the master connection. this allows pool checkouts/checkins to work as expected without interacting with the master/slave connections.
Rails 4 support
Hook into rails db:* tasks load_config so seamless_database_pool can remove itself for tasks that are based on the adapter name.
Merge branch 'master' of https://github.com/red5studios/seamless_database_pool into red5studios-master
Merge branch 'rails4' of https://github.com/mobi/seamless_database_pool into mobi-rails4
Update connection adapter specs to use mysql2 gem instead of old mysql gem.
update history and version number