Implement user registration feature

* Add users/new action and view
* Add users/create action
* Add link to sign up in sign in page

config/routes.rb

@@ -1,4 +1,6 @@
 Scube::Application.routes.draw do
+  resources :users, :only => [:new, :create]
+
   resources :sessions, :only => [:new, :create]
 
   resources :tracks do