Remove all email signups AB test code

This pull request removes all the code for the email signups test since the test is expiring.

The test will be coming back in another form so we can verify the results.

Please confirm that these code removals do not affect any other ab tests.

Thanks!

![code-34](https://f.cloud.github.com/assets/1170410/1985752/2d7711e8-8443-11e3-92fc-2c914afa3e1b.gif)