v0.2.0 released

## Changes
### mangeticod
* Cython-based bencoder.pyx is  used instead of our own pure Python solution.
* `--node-addr` commandline argument added.
* TCP QUICKACK is automatically enabled (instead of by default) so that magneticod can work on macOS as well.
* Database index added for `info_hash` column of `torrents` table.

### magneticow
* Some small performance improvements for search.

initial commit