example interceptor commit
Merge branch 'master' into interceptor-introduction

Resolved Conflicts:
	todo-yeoman-front-end/app/scripts/app.js
	todo-yeoman-front-end/app/scripts/controllers/login_controller.js
	todo-yeoman-front-end/app/scripts/services/session_service.js
Added Interceptor for adding `auth-token` to request headers.
Merge branch 'master' into interceptor-introduction

Resolved Conflicts:
	todo-yeoman-front-end/app/index.html
	todo-yeoman-front-end/app/scripts/app.js
Removed code for updating header on route change start.
Moved control to interceptor.
Merge branch 'interceptor-introduction'
Changes in Login Form :-
Shows error messages form Server.
Changes inputs colors on submit if invalid.
Validations for Login Form.
Added form submission changes code

Added changes for calling validations before submission of the form.
disable invalid credentials message on submit