Removed Serialization spec.

This was failing since the default for to_json change from Rails 3 to 4
to not include the root element
(ActiveRecord::Base.include_root_in_json=false). This doesn't seem
to be testing anything in the Cequel code itself, so we should
eliminate this external dependency.
Getting rails-observers temporarily from private branch.

I need to do this for now because rails-observers in incompatible
with the 4.0 release of the Rails stack (e.g. ActiveRecord, ActiveSupport)
because it's pegged to the beta. This is causing problems in the Cequel
gem which we are trying to upgrade to 4.0, but needs consistent versions
of these dependencies. This hack is temporary until the rails 4.0
upgrade pull request is merged in the source repo.