cleanups to the test suite

You couldn't really run just one test file at a time.  The helper
didn't add the root dir to the load path so you couldn't run tests
from within a subdir of the testdir.

* added root dir to load path in helper
* didn't require all of and-son in the helper
 * tests now require the pieces of and-son they need
* added pry for debugging
* pluralized test contexts and file names