Fix use of threading.Event for Python 2.6 and clear connected state.

threading.Event's wait method returns None on python pre 2.7, which means all
searches would fail. This also corrects that fact that we weren't clearing the
connected threading event on disconnects. I did not add any tests for this at
this time as I just want to get the fix out.
Add caveat about static in sound test file.

Add a note saying that the purpose of the "aplay ... Front_Center.wav" line is merely to test whether the sound works or not, rather than to test its quality.

Anecdotally, I had very static-y sound from the aplay command, which prompted me to incorrectly believe that my sound would not work with Mopidy. As it turns out, the sound works fine using Mopidy or gstreamer. This note will hopefully keep other Mopidy users from thinking their sound is broken when it is not. (I ended up installing armhf version and trying to use despotify, which didn't work, before coming back to Mopidy.)
Merge pull request #294 from jeremybmerrill/patch-1

Add caveat about static in sound test file.
Add timestamp and duration to all spotify buffers.

This fixes the issue where pausing playback would show the time of the last
timestamped buffer instead of the current time. We also make sure to reset the
time when we start a new track. This was done by overriding the play method on
the session manager as it is also used for pausing, resuming and stopping.

Ideally this should probably be reworked to avoid the gst import in
mopidy.backends.spotify.playback, but for now this should do.
Fix racecondition triggered KeyError in our DebugThread.
Update authors list
spotify: Remove gst import from spotify.playback module
Revert "spotify: Remove gst import from spotify.playback module"

This reverts commit 0459f037a4e51886ccfbbdb59e7b70cea60e5f03.
spotify: Remove gst import from spotify.playback module
Revert "spotify: Remove gst import from spotify.playback module"

This reverts commit b4028e9c577c03277cfc39b24b070fd4868a3847.
docs: Add woutervanwijk's web client
settings: Update settings validator to support empty iterables.
stream backend: Add StreamBackend, fixes #151

Adds a basic streaming backend simply handles streaming audio and nothing else.
I.e. no metadata beyond the URI we where given. #270 still needs to be solved
for actual metadata to make sense in this backend.
core: Update BaseLibraryProvider to not require refresh, search or find_exact.

These methods may now return None, and the core code has been updated to filter
out missing SearchResults.
core: Update tests with cases for filtering out None results.
audio: Move supported URI checking to mopidy.audio.utils

In order to avoid gstreamer imports leaking into more of our code I'm moving
this to a new utils class in audio.
scanner: Support symlinks
Merge pull request #295 from adamcik/feature/streaming-backend

Add basic streaming backend support.
Fix flake8 warnings
docs: Document new backend