Start of a debian package for charmstore

PR:
1. Edit buildpackage.sh and change the last line to a PPA to which you can write. 
2. Make sure you have DEBEMAIL set for signing.
3. Install build dependencies (see README.md).
4. Run sh buildpackage.sh.
It's not completely clear to me in what cases we want to run all of this instead of just buildpackage.