Ensure BGRA pixel encoding, mention it in the documentation
mpv-nordlicht.lua: Set process niceness to 10
Vagrant: Mount host's .gnupg folder into VM to enable package signing
Vagrant: Add python-software-properties to Debian bootstrapping script

This package contains add-apt-repository, which is used to add PPAs.
README: Link to PPA for Ubuntu installation
Now that mpv 0.3.6 is out, don't refer to the commit anymore
Add simple library testsuite and update tool testsuite

Both should be run with "make test" from the build directory and require a
"video.mp4" to be present.
Fix a few bugs found writing the test suite

- deal with NULL arguments
- allow video URLs as input (awesome!)
- correctly honor the modifiable flag
Move test/ to tests/, following a convention
Tool: Output format is controlled by output filename extension

The two supported formats are "png" and "bgra".
Fix typo in .gitignore
--live switch is no longer needed in mpv integrations
Style improvements
Introduce nordlicht_set_style to replace the "live" switch

This will probably be removed later, when generation will be both fast
and "live".
README: Condense mpv documentation
Add basic strategy tests to library test suite
Add a more concise library example, since main.c got too large
Add three examples to --help and man page

Also, add an author's note (The Pragmatic Programmer, Tip 70: "Sign your
work").
mpv-nordlicht.lua: Wait 0.5 seconds for the "convert" commands to finish
Add a "Contributing" section to the README