docs: Add Mopidy-GMusic (fix #355)
docs: Add Mopidy-SomaFM (fix #509)
config: Deserialize Secret to unicode (fix #473)

MPD, Scrobbler, and Spotify extensions have been reviewed for need for changes
due to this, without anything being found.
Merge pull request #510 from jodal/feature/unicode-secrets

config: Deserialize Secret to unicode (fix #473)
docs: Mopidy-GMusic is now on PyPI
Fix too broad truthness test (fix #501)

This caused TlTracks with tlid=0 to be sent to HTTP clients without the tlid
field.
Remove support for running Python on the mopidy/ dir

It doesn't make sense to run Mopidy without extensions registered, thus you'll
need to use setuptools and to run `python setup.py develop` anyway. Doing so
makes running `mopidy` from anywhere in the development virtualenv work,
removing any need for running `python mopidy/`.
Create empty config file if none found (see #467)

We already had code in place for this, but it was run after the config
validation, so on a new installation Mopidy would fail because of missing
config values before the config file was created.
main: Split main() function in two

By separating the teardown procedures for errors that happens before and after
actors are started, we get a lot less output when failing on config errors.
This makes the config errors the last lines printed by the `mopidy` command,
making them easier to spot.

Related to #467
Merge pull request #511 from jodal/feature/split-main-func

main: Split main() function in two
main: Don't be verbose on CTRL+C before starting actors
Merge branch 'feature/split-main-func' into develop
main: Reorder/rename functions
js: Upgrade Bane from 0.4.0 to 1.0.0
js: Upgrade When.js from 2.0.0 to 2.4.0
js: Upgrade faye-websocket from 0.4.4 to 0.7.0
js: Upgrade devDependencies
js: Bump npm package version
js: Build updated mopidy.js
Adding playback error handling, by notifying the tracklist about it, and therefore, the backend