Support the latest rails (4.2.0beta4 at time of commit)

Rails >= 4.2 has changed the method arity of
_compute_redirect_to_location from (options) to
(*args). The validation inside then expects two
parameters: request, options. This commit handles
these changes.
Merge pull request #4 from dimroc/master

Support the rails 4.2 (4.2.0beta4 at time of commit)