Rails 4.1 & Ruby 2 Compatibility Update

A series of updates for Rails 4.1 and Ruby 2.x (tested on Ruby 2.1.1, but the error could appear in earlier versions).

Rails 4.1 Updates:

* Gems specified tied to Rails 4.0.x series
* ActiveRecord change to [disallow scopes named :public, :protected, or :private](https://github.com/rails/rails/commit/815c9deae8de557688e1c99aabe30454bcbe5970)

Ruby 2.x Updates:

* Remove two uses of `return` where it was used in a block, these were causing `LocalJumpError: unexpected return` errors in the tests, I can't see where this was updated in the Ruby source but it seems from SO threads that it was around the Ruby 2.0 release.

* Included Ruby 2.1 in the versions Travis tests against.

All tests are passing and the changed scope seems not to appear elsewhere in the source code, however this will obviously be a breaking change.

— Chris