Changing the way of alchemy menubar rendering.

From now we let rails render a partial for the menubar, removed the helper ´alchemy_menu_bar´ and do not build the bar with javascript anymore.

Old usage:  <%= alchemy_menu_bar %>
New usage: <%= render "alchemy/menubar" %>
Updates jasmine installation.
Also run jasmine specs with default rake task.
Complete coverage of `Admin::ElementsController`
Refactors the page dirty check.

- Don't show the please wait overlay, if page is dirty.
- Delete the onbeforeunload event, if the confirm dialog is used.
- Use $.show() and $.hide() to toggle the please wait overlay.
Bumps version to 3.0.0.beta1