[tor-dev] Leekspin and Stem descriptor creation

Hi Isis. For kicks and giggles this weekend I added the ability for Stem to create descriptors...

https://stem.torproject.org/tutorials/mirror_mirror_on_the_wall.html#can-i-c... https://gitweb.torproject.org/stem.git/commit/?id=b2a54ad

This is something Stem has always been able to do but it was buried in our testing helpers. Now descriptor subclasses have a static create() and content() method.

This *doesn't* yet support signing descriptors. I'm looking into that next. To that end I took a peek today at leekspin (https://pypi.python.org/pypi/leekspin) and... damn. Beautiful work! Besides the crypto are there any other aspects of your library you think we should incorporate?

Cheers! -Damian