Tests needed for recent spec updates

[bvisness]

Both the core and JS API specs have seen several updates over the past several weeks, and these updates need to be reflected in spec tests.

Specifically:

• Update JS API to handle index types #75 and Fix small issues in the JS API #78
• Fix many miscellaneous spec problems #77
• Restrict offsets to index type's range in validation #79

I suppose we probably need to wait until those changes are all merged before merging any new tests, though.