Generate User scaffold
Add bcrypt to Gemfile for User.password field
Add mocha to Gemfile
Add various notes
Add email and password validations to User
Remove 'length' validation from User.password.

Length validation is done by PasswordFormatValidator.
Add notes/todo.txt file
Email format validator now does not validate nil value
Add refactor validators TODO
Password format validator now does not validate nil value
Remove superfluous check for nil
Email format validator now does not validate empty value
Password format validator now does not validate empty value
Add TODO to map db exceptions to model errors
Add link to sign up page