Fix Travis CI builds

Author: polarina

.travis.yml

@@ -17,7 +17,7 @@ before_install:
       export CABAL=cabal-1.18
       export PATH=/opt/ghc/$GHCVER/bin:$PATH
     fi
-  - wget http://libsdl.org/release/SDL2-2.0.3.tar.gz -O - | tar xz
+  - wget http://libsdl.org/release/SDL2-2.0.4.tar.gz -O - | tar xz
   - cd SDL2-2.0.3 && ./configure && make -j && sudo make install && cd ..
   - cabal install --only-d