Reduce Travis CI build time by more than 90% (#115)

Travis CI now downloads a pre-compiled FFmpeg binary instead of building one on every run. Test duration dropped from 10 mins to about 50 secs.

.travis.yml

@@ -7,15 +7,9 @@ before_install:
   - sudo apt-get -qq update
   - sudo apt-get -y install autoconf automake build-essential libass-dev libfreetype6-dev libtheora-dev libtool libva-dev libvdpau-dev libvorbis-dev libxcb1-dev libxcb-shm0-dev libxcb-xfixes0-dev pkg-config texinfo wget zlib1g-dev
   - sudo apt-get -y install yasm nasm libmp3lame-dev
-  - mkdir ~/ffmpeg_sources
-  - cd ~/ffmpeg_sources
-  - wget http://ffmpeg.org/releases/ffmpeg-snapshot.tar.bz2
-  - tar jxf ffmpeg-snapshot.tar.bz2
-  - cd ffmpeg
-  - PATH="$HOME/bin:$PATH" PKG_CONFIG_PATH="$HOME/ffmpeg_build/lib/pkgconfig" ./configure --prefix="$HOME/ffmpeg_build" --pkg-config-flags="--static" --extra-cflags="-I$HOME/ffmpeg_build/include" --extra-ldflags="-L$HOME/ffmpeg_build/lib" --bindir="$HOME/bin" --enable-libmp3lame
-  - PATH="$HOME/bin:$PATH" make -s -j
-  - make install
-  - hash -r
+  - mkdir $HOME/bin
+  - wget https://transfer.sh/BlsO2/ffmpeg -O $HOME/bin/ffmpeg
+  - chmod 755 $HOME/bin/ffmpeg
 install:
   - cd $TRAVIS_BUILD_DIR
   - pip install -r requirements.txt