OTHER: Fix travis with a big hammer.

Should be cleaned up later, but this'll do for now.
OTHER: Update name/keywords in desktop file.
OTHER: Improve travis config slightly.

...aka lipstick on a pig.
OTHER: Update README.
OTHER: Update playlist text/style.
OTHER: Remove silly _ prefixes for private members.
OTHER: Remove unused volume button class.
OTHER: Make playback label clickable for search.
OTHER: Remove unused declarations.
OTHER: Unbreak entry_changed signal handler for playlist model.
OTHER: Just say 'Abraca' in playback label before playback starts.
OTHER: Silence incompatible pointer type warning.
unify playlist entry creation and population

Prior to this commit, Abraca first creates cells with "insert" or "add"
and then separately populates them using "set".

Certain accessibility services intercept the insertion before anything
was stored, examining the cell content via AbracaPlaylistMode.get_value.
This triggers requesting song information from xmms2, if needed,
resulting in an erroneous request of media id 0, which leads to
seemingly empty entries in the playlist.

Accessibility tools that trigger this behaviour are for example screen
magnifiers or even gnome-shell 3.12 itself, as long as it is not built
including the patch to initialize at-spi on demand
<https://bugzilla.gnome.org/show_bug.cgi?id=730118>.

This commit unifies insertion and population to a single call to
"insert_with_values", making interception impossible in between.
add Dominik Fischer to AUTHORS