Rails 4 support

Hi,

We needed to use masq in a new project, so we adapted it to work with Rails 4.
Obviously this branch is incomplete as we need to remove dependencies from git when Rails will be in rc, but we will finally not use OpenID in the project, so we won't be able to work on the fork anymore.

All tests pass, although a few could be added to verify strong_parameters works as expected (we only added this to one test). There might also still be troubles with calls to `h()` in the views, which is deprecated since Rails 3 and not available in Rails 4 I think.

 I hope you can leverage this work to support Rails 4 when it is released.