Add missing test dependences to Appraisals

Since as of commit 2748b750873faf587c78d7a71f6c725b0fd4252a, we no longer install dependencies inside of the Rails app that is generated and used to run all of the tests, we have to require all of the dependencies that the app would install inside of the appropriate Appraisals. This will unbreak the test suite (as currently it's broken, whoops ;))

This was mostly straightforward except for some workarounds with the turn gem:

* Rails 3.1 requires two versions of turn depending on which Ruby version you're using. On 1.9.2, it uses turn 0.9.2; after 1.9.2, it uses ~> 0.9.3. To accommodate this we have to have two versions of the
  Rails 3.1 appraisal which declare the different turn versions.
* Rails 3.1 also loads the turn gem even if, in the Gemfile for the app, turn is declared with `require: false`. This causes a problem while running our tests because turn actually requires minitest/autorun, which adds a hook so when Ruby exits, Minitest tests are run. Because we're already using RSpec, Minitest will try to re-run the `rspec` command we ran within a Minitest environment. This will fail since we are using RSpec-specific command line options to run the tests. Unfortunately there's no way to shut off minitest/autorun after it's been required, so we have to monkey-patch Minitest's #run method so it's a no-op.