Add authentication and User model

* Add User model
* Add SessionsController
* Add password authentication on User
* Request authentication for all actions except sign in
* Add some helpers for ApplicationController
* Update features to work with mandatory authentication

spec/views/sessions/new.html.haml_spec.rb

@@ -0,0 +1,26 @@
+require 'spec_helper'
+
+describe 'sessions/new.html.haml' do
+  it 'renders a form to sign in' do
+    render
+    rendered.should \
+      have_selector("form[method=post][action='#{sessions_path}']")
+    rendered.should have_selector('input[type=submit]')
+  end
+
+  it 'renders a text field with a label for the mail address' do
+    render
+    rendered.should \
+      have_selector("input[type=text][name='session[email]']")
+    rendered.should \
+      have_selector('label[for=session_email]', :text => 'Email')
+  end
+
+  it 'renders a password field with a label for the password' do
+    render
+    rendered.should \
+      have_selector("input[type=password][name='session[password]']")
+    rendered.should \
+      have_selector('label[for=session_password]', :text => 'Password')
+  end
+end