Implement custom strategy for OmniAuth

A custom strategy has been implemented that tells OmniAuth how to authenticate against the Chandelier suite.
Install OmniAuth

OmniAuth is a flexible authentication solution, and works with our custom strategy to authenticate users against the Chandelier suite's AAA service.
Generate SessionsController

This controller handles the sign in and out of users.
Implement SessionsController

The session management has been implemented in a very basic way. Specs for most actions verify their behavior, and routes have been set up to point to the OAuth flows.
Make static_pages#private actually private

A before filter has been added to allow only signed in users to see the page. All other users are redirected to the sign in form.
Add error message to authentication template

A paragraph has been added that provides a place where error messages can be displayed.
Fix bug in application layout

An unknown variable error occurred with the old version of the template, since the flash message was not accessed properly.
Specify format for OAuth callback

The server expects the client to request JSON, so we add the format to the callback URL.
Include original URL in auth redirect

When redirecting to the authentication provider, include the original url so that the user can get redirected after authentication.
Include x86 gems

Once of the development machines runs a 32bit Windows, and for convenience the missing gems have been added to the Gemfile.lock.
Merge branch 'feature/integrate-oauth' into develop