use a shorter gemset name

The zsh prompt was getting a bit large when showing the ruby version and gemset
name, so using a shorter gemset name saves some space.
Gemfile should support both linux and darwin
add a User model
add unit tests: User responses

* User responds to :name
* User responds to :email
validate presence of User name/email
add addition name and email validations

* name
    - lenth <= 50 characters
* email
    - format follows simple email regex
    - uniqueness (case insensitive)
add index to users email
downcase email before saving to database
add gem bcrypt-ruby to Gemfile
add test user should respond to password_digest
add migration add_password_digest_to_users
add hass_secure_password and tests to User
add tests for user.authenticate and password length

* add tests for user.authenticate
    - return the user on correct password
    - return false on incorrect pasword
* add test for minimum password length
    - password must be 6 characters or more
* refactor line order in User model to group email regex and validation
add test for and refactor email.downcase
add test and modify regex for emails like foo@bar..com