License for Erebus

Hi Cristobal, just realized that I forgot to have us set up the license and copyright for Erebus. Oops. There's two bits for this: the copyright holder and the license itself.

For Stem copyright it's jointly held by me and Tor (the non-profit organization). My suggestion would be for it to be you, me, and Tor. Happy to discuss this though if you'd like something else.

As for the license Tor mostly uses BSD (in case you're unfamiliar that's in the same family of very open licenses as Apache). For Stem I've used LGPLv3 but that's been a patter of personal taste. Either BSD or GPL is up to you. If you'd like something else then again happy to chat.

In terms of the repository changes we need the following...

1. Add a LICENSE file, similar to what Stem does.

2. At the start of every file with source code add a header saying the following...

# Copyright 2015, Cristobal Leiva, Damian Johnson and The Tor Project
# See LICENSE for licensing information

After this done I should follow this up with moving the repository to git.torproject.org and adding a trac component. That is, unless you'd like to keep it on GitHub. Again, up to you.