docs: Should install gstreamer0.10-alsa before using alsasink
New flake8 version with new checks to conform to
docs: Make 'mopidy config' more prominent
docs: Add page for the Debian package
docs: Fix typo
docs: Fix typo
core: Fix shadowed import

Catched by new stricter flake8
Pause gstreamer when buffering

When the `playbin2` pipeline is in `PLAYING` state and its buffer is empty the
pipeline will consume arriving data immediately. If the source is an HTTP
stream this leads to choppy playback. To fix this we pause playing when the
buffer is nearly empty and wait for it to fill up until we resume playing. This
approach is recommended in the gstreamer manual [1].

We might want to extract the hard-coded 10% mark and make it configurable.

[1]: http://gstreamer.freedesktop.org/data/doc/gstreamer/head/manual/html/chapter-buffering.html
Set buffer properties of gstreamer pipeline

Manually set the `playbin2` buffer properties to their default values. The
default values are not documented but hard-coded in gstreamer [1].

This is a starting point for making these properties configurable. For example
we might want higher values on system with unsteady network connection.

[1]: http://cgit.freedesktop.org/gstreamer/gst-plugins-base/tree/gst/playback/gsturidecodebin.c?h=0.10#n1714