Do not use action caching for pages#show anymore.

We now use fragment caching  on the pages#show template and send etag and cache-control headers.
Adds cache_digests support.
Add to_partial_path to models.
Uses Rails 4-0-stable branch
CacheDigests support for cells and essences.
Adds template_tracker specs.
Cache all essence views and adds specs
Use content as local variable in essence views again.

We cannot use the partial name, this causes a lot of problems with existing helpers and specs.
Refactors admin/contents_helper
Fixes errors attachments controllers and template tracker specs
Fixes essence view specs.
Changes how the pages controller gets the layout to render.

No more class method, instead the layout_for_page method gets called in render call.
Fix cells factory name attribute.
Refactors the render_elements helper.
Refactors render_element helper.
Use render_page_layout in pages#show, to have the standard layout fallback working.
Adds spec for attachment#restricted?
Adds a temporary fix to suppress phantomjs warning on os x mavericks.
Adds specs for page model.
Specs all essence views.