Uses submodule references and runs tests automatically.

Submodule references are now used to reference dependencies.

Xcode .xcconfig files are used to handle any custom build settings.
These are easier to diff/merge in git than the xcodeproj files.

Fixes an issue with the ARTestCase runUntilStop method. In some
circumstances the tests will fail and this method turns into an infinite
loop.  Added a timeout value with a default of 20 seconds.

Fixes issues with handling of RAILS_BASE_URL when it includes percent
encoding. Due to issues with how Xcode handles .xcconfig files it was
necessary to pass the RAILS_BASE_URL into the test environment as a
percent encoded string.  The string handling logic in the unit tests
fails when presented with a percent encoded string.