Normalize email address during registration

### What is the problem / feature ?

Email addresses were not being normalized on registration.  

### How did it get fixed / implemented ?

Added a call to lowercase the email address on the way through the registration form.

### How can someone test / see it ?

- Register with an uppercased email address is now forced to lowercase.
- Added a migration to lowercase all email addresses as well as remove any users with duplicate accounts.

*Here is a cute baby animal picture for your troubles...*

![buisnesscorgi](https://cloud.githubusercontent.com/assets/824194/2650550/ef4da0e0-bf74-11e3-9f78-96b427bb7de9.jpg)