Rails 4

A few changes worth calling out:

1. Using a rails 4 branch of the i18n-active_record. We had this forked in numerex, but hadn't made any changes. The latest master on the original fork (https://github.com/svenfuchs/i18n-active_record) works with Rails 4, but there's no released version that does. It seems like this is a somewhat abandoned project, so maybe we should look for alternatives.

2. Added a dummy app under the test dir since that's what engines do by default now. Will make it easier to test different rails versions going forward. We can even use something like appraisal (https://github.com/thoughtbot/appraisal) if warranted.

3. The only real change to production code here is the use of HTTP verbs instead of "match" in the routes file.