Spec reorganization

A few things going on here:

* Split out individual pieces of the spec helper file into support
  files. This should make it easier to upgrade rspec by regen'ing
  the spec helper if we ever need to.
* Removed rspec-rails and added capybara. The former was silently
  suppressing view output in controller specs based on the name of
  the folder that the spec file was in. I'm all for convention over
  configuration, but ... come on.
Regenerate spec helper and restore rspec-rails

Looks like we need rspec-rails (or some subset thereof) for the `get`
and `post` helpers in the controller specs.
Clean up and use spec helpers
Add place order feature spec

and update the notion of order due date