Drop code that only existed to support Rails 2

Drop code that only existed to support Rails 2

We dropped support for Rails 2 back in the 3.0b release, so there is no
need to keep this crud lying around.

If somebody attempts to use the Gem with Rails 2, it should explode with
a NoMethodError when we call ActiveSupport.on_load(:action_view), which
seems fair enough.

Signed-off-by: Wincent Colaiuta <win@wincent.com>