Added additional tests for validation. Shifted some code around between go_schema_test and schema_test.

Summary:
Fixed a bug where we weren't setting Interleave from struct field tag
"interleave".

Test Plan: this commit adds unittests! hurrah.

Reviewers: andybons

Reviewed By: andybons

Differential Revision: http://phabricator.andybons.com/D13