Travis: Use custom libtorrent formula and bottle for OSX.

Caches libtorrent 1.0.10 built with c++11 enabled.

.travis.yml

@@ -30,7 +30,10 @@ notifications:
 
 # container-based builds
 #sudo: false
-cache: ccache
+cache:
+  ccache: true
+  directories:
+    - $HOME/hombebrew_cache
 
 # opt-in Ubuntu Trusty
 sudo: required
@@ -117,12 +120,25 @@ install:
     fi
   - |
     if [ "$TRAVIS_OS_NAME" = "osx" ]; then
+      mkdir -p "$HOME/hombebrew_cache" ;
+      wget http://builds.shiki.hu/homebrew/version ;
+      if ! cmp --quiet "version" "$HOME/hombebrew_cache/version" ; then
+        echo "Cached files are different from server. Downloading new ones." ;
+        cp "version" $HOME/hombebrew_cache ;
+        cd "$HOME/hombebrew_cache" ;
+        wget http://builds.shiki.hu/homebrew/libtorrent-rasterbar.rb ;
+        wget http://builds.shiki.hu/homebrew/libtorrent-rasterbar-1.0.10.yosemite.bottle.tar.gz ;
+      fi
+      
       # dependencies
       brew update > /dev/null ;
       brew install colormake ccache ;
       brew outdated "pkg-config" || brew upgrade "pkg-config" ;
-      # libtorrent-rasterbar 1.0.9
+      # Copy custom libtorrent bottle to homebrew's cache so it can find and install it
-      brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/477d5060fa093883204d70323965375353e03084/Formula/libtorrent-rasterbar.rb ;
+      # Also install our custom libtorrent formula by passing the local path to it
+      # These 2 files are restored from Travis' cache.
+      cp "$HOME/hombebrew_cache/libtorrent-rasterbar-1.0.10.yosemite.bottle.tar.gz" "$(brew --cache)" ;
+      brew install "$HOME/hombebrew_cache/libtorrent-rasterbar.rb" ;
 
       # Qt
       if [ "$qt" = 4 ]; then brew install qt && ln -s /usr/local/Cellar/qt/4.8.7_2/plugins /usr/local ; fi ;