Remove explicit dependency on activesupport

[jaredbeck]

activerecord depends on activesupport, so there's no need for us
to explicitly depend on it.

[batter]

True, ActiveRecord does depend on ActiveSupport, so perhaps the explicit dependency is unecessary, however, there are parts of the code where we utilize ActiveSupport directly, and if at some point in the future ActiveSupport was removed as a dependency for ActiveRecord (doubtful this would happen anytime soon if at all), then it would break the code.

I always think it's better to be explicit about these things. Sorry for not chiming in sooner.

[jaredbeck]

.. if at some point in the future ActiveSupport was removed as a dependency for ActiveRecord ..

Seems unlikely, but if you want to revert this it's fine with me.