Add basic ActionMailer

 * HAML and ERB email views

Add user scaffold

Send welcome email

 * Add tests

 * Add test fixture

 * Fix email views

 * Add user migration

Throw exception on synchronous mailer errors
Merge conflict - fix config/routes.rb since matt-e modified the chirp route
Merge pull request #5 from marcbowes/master

Merge in Ronen's user model