vimiv: 0.7.2 -> 0.7.3

Bugfix release with the following fixes:

 * Fix thumbnail creation for input files with dot
 * Use native python to generate list of external commands
 * Do not use commandline arguments in test mode
 * Catch broken symlinks in the library and filter them

So everything but the last item is essentially what we had in
fixes.patch, hence we cane remove it.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>