Add module tests

[rahearn]

closes #15

Adds tests for all of the existing modules, attempting to exercise all outputs and input variables.

Only the s3 module is actually creating real infrastructure. The rest of the modules are mocking the cloudfoundry provider to speed test runs significantly and enable testing modules that require either multiple spaces or more memory than we can dedicate to CI runs.

[mogul]

Good start! Looking forward to seeing how this develops.

[asteel-gsa]

Very cool! This looks awesome!

[pauldoomgov]

One non-blocking suggestion. This is really great! Making Terraform testable with native capabilities is so much slicker than alternatives!

[pauldoomgov]

LGTM!