Fix situation where MANIFEST comment is empty

Hi Rik,

If you have the following line:

    # ABSTRACT:

Then you get the next line of code as the abstract. I think the intention of the code was to not match at this point, so the abstract would be extracted from the pod. This change does that.

Possibly it should warn if the above case if found, "You doofus, you've got a blank ABSTRACT".

Sorry I didn't add a test - I'm supposed to be playing with the kids, which I will be once I create this pull request. Oh and do a release to fix my dist :-)

Cheers,
Neil