Carry on to "first tests"

I asked Dave to let me have a go at this. With his help I added script for running the tests automatically and I added another puny little test to it.

Regarding line 50 (missing.append) and whimboo's question if manifestparser does the checks already (from the previous pull):

    I just had a look at the TestManifest class of manifestparser.py and it's true it makes checks if a test exists, but unlike here, it just ignores it, if the test doesn't exist.

    https://github.com/mozilla/mozbase/blob/master/manifestdestiny/manifestparser/manifestparser.py#l750

I assume that is the reason for this line.