rails4: first steps to upgrade from rails 3.2 to rails 4.

* updating gems using 'bundle update' and resolving dependency issues.
* resolving worst deprecation issues.
* now being able to run the specs using 'bundle exec rake'.
* now being able to start a 'rails server'.

Trello: https://trello.com/c/Dlio0wG9/281-rails-4
Railscast: http://railscasts.com/episodes/415-upgrading-to-rails-4