Add spec parser tests up to function types.
Rename MapType.Type to MapType.Value.
Add the ids helper function for tests.
Add more spec tests. Up to, but not including, iota.
Add more spec tests.

I also moved the test tables out of the function to reduce their
indentation by one level.
Rename fields from "Identifiers" to the shorter, more consistent, "Names."
Merge pull request #23 from velour/dev/eaburns

Add tests based on examples in the spec.