Create admin area - #4

- Create admin directory under controllers;
- Create Admin::AdminController;
- Create Admin::HomeController with a welcome action and view.
Install Bootstrap - #4

- Install jQuery version 1.10.2;
- Install Bootstrap.
Add layout page for admin area - #4
Add Bootstrap stylesheet and script on admin layout page - #4
Include Modernizr on top of layout pages - #3
Install and configure Devise gem - #5
Generate User Devise model - #5
Describe user sign in feature - #5
Implement user sign in feature - #5

- Implement feature;
- Style header for admin section;
- Apply Bootstrap styles to form.
Add Bootstrap Jumbotron to admin welcome page
Add mailer settings
Fix seed data
Describe user sign out feature - #6
Implement user sign out feature - #6
Describe user password recovery feature - #7
Implement user password recovery feature - #7
Add validations on password recovery feature - #7
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.