WIP: Trying to set up tests.

JSON doesn't unmarshall correctly in line 41 of `main_test.go`.
Export schema fields
Merge pull request #1 from cupcake/fix-playground

Export schema fields
Make improvements after review.

+ Place test resources in the repo using a git submodule.
+ Move the package to the root of the repo.
+ Raise test errors immediately within the function used by walk.
+ Make test errors more informative.
Ask if the git submodule is installed if test resources are missing.
Fix mistake where submodule wasn't included in .gitmodules.
Fix mistake in submodule setup instructions.
Immediately check for the test resource dir.

Also suggest one command instead of two for installing submodules.
Log number of successes and failures.
Fix incorrect help message; tighten up style.
Merge pull request #2 from cupcake/playground

Set up tests.