ignored assertion macros

[kellyredding]

• look at 1.8.7 test-unit, 1.9 minitest
• do some meth missing action for any assertion helpers we are choosing to not implement
• have them raise a new type of result called 'ignored' or something
• this is so that it won't break backwards compatibility, but at the same time we don't have to implement every little helper the old libs do.
• if we ever decide to implement more macros, we just do it and take them out of the ignored ones.

[jcredding]

This is in master now, I've implemented a few more macros (empty, nil and includes) but haven't tested them yet. I'll test them as I re-work the assertion tests for basic test unit.