Remove spring preloader.

Spring seems a little too bleeding-edge at this point. It makes most
things faster, but with the penalty of introducing mysterious bugs
that are only solved by manually restarting the spring process.
Introduce helper for simplifying nested layouts.

Break application layout into separate, nested base and application
layouts.
Merge branch 'master' into rails-3-2

Conflicts:
	Gemfile.lock
bundle update