add any roles per user

example: https://github.com/ryanb/cancan/wiki/Role-Based-Authorization
add gem 'cancan' use authorization library
add cancan ability.rb authorization

the gem wiki : https://github.com/ryanb/cancan
add home layout and modify sigin page
add user_navbar css style and rewrite user nav html
Merge branch 'role_based_authorization'
Merge branch 'master' of https://github.com/JeskTop/giggle

Conflicts:
	db/schema.rb