Add some additional specs to the pages controller.

Add response code and layout specs to the pages_controller#home.  These
are probably not needed, but were written trying to track down another
issue and can't hurt to be left in.
Add some basic view specs.

Add some basic view specs for the home page and application layout.
Use correct name of signed_in? helper method.

Use correct name of signed_in? helper method in the application layout.