Libav 10 was released, so we can enable testing the stable Libav version
again.
FFmpeg 2.2 was also released, but since we still support 2.1.4, we stick
with the older version. This is better for testing.
I overlooked the fact that the ffmpeg/libav build system only supports `--cc`
and completly ignores $CC. Hopefully this makes the build times a little
faster.
Fixes#332
Travis-CI [1] is a continous integration cloud service. It is free for
open-source projects and tigthly integrated tiwh GitHub so there is really
no reason for us not use it. :)
For now we are going to do a total of 4 builds, mainly to test ffmpeg/libav
API breakage:
* ffmpeg-stable, libass-stable
* ffmpeg-git, libass-stable
* libav-stable, libass-stable
* libav-git, libass-stable
The compiler that is currently used is clang for two reasons:
* running 8 build targets would be quite wasteful and take a long time
* clang is less tested and used during development than gcc (especially on
linux)
Currently Travis doesn't support OS X environments alongside Linux ones [2].
When it will, we will add a fifth build target to test OS X compilation
breakage.
README was moved to markdown to add the little build status image. I ran some
tests with my GitHub fork and couldn't get images to show up using ReStructured
Text.
[1]: https://github.com/travis-ci/travis-ci
[2]: travis-ci/travis-ci#216
