Describe user creation feature - #8
Remove User first and last name and add a name column
Install and configure RoleModel gem - #8

- Install RoleModel gem;
- Add :roles_mask attribute to User;
- Include RoleModel module in User;
- Add :super_admin and :admin as valid roles.
Install and configure CanCan gem - #8

- Install CanCan gem;
- Generate the CanCan::Ability class.
Implement user creation feature - #8

- Implement feature;
- Improve error feedback on layout.
Fix register_user helper
Describe user confirmation feature - #9
Implement user confirmation feature - #9