Travis: Try to cache downloaded files to work around sf.net sucking

.travis-deps.sh

@@ -20,6 +20,8 @@ if [ "$TRAVIS_OS_NAME" = linux -o -z "$TRAVIS_OS_NAME" ]; then
     curl http://www.cmake.org/files/v2.8/cmake-2.8.11-Linux-i386.tar.gz \
         | sudo tar -xz -C /usr/local --strip-components=1
 elif [ "$TRAVIS_OS_NAME" = osx ]; then
+    export HOMEBREW_CACHE="$PWD/.homebrew-cache"
+    mkdir -p "$HOMEBREW_CACHE"
     brew tap homebrew/versions
     brew install qt5 glfw3 pkgconfig
 fi

.travis.yml

@@ -4,7 +4,10 @@ os:
 
 language: cpp
 
-cache: apt
+cache:
+  apt: true
+  directories:
+    - .homebrew-cache
 
 before_install:
  - sh .travis-deps.sh