WIP: Profiles for mentors

WIP pull request for mentor profiles.

What we have done: 
-Added additional bio and mentor interest text fields for the mentor profile form.
-Added javascript so that the fields autofill after email address is entered in the case of a repeat mentor.
-Added gravatar profile pictures for users for easier identification.
-Added a profile that users can clickthrough in order to learn more. This replaces the direct link to Twitter in current version.

Still Needs Work:
-Updating of user information needs further testing.
-Have not yet done testing on user activation with the mailer.