Fix Travis OSX build.

.travis/before_install.sh

@@ -9,4 +9,5 @@ if [ "$TRAVIS_OS_NAME" = "linux" ]; then
 elif [ "$TRAVIS_OS_NAME" = "osx" ]; then
   brew update
   brew upgrade cmake
+  brew install libsndfile
 fi

.travis/install.sh

@@ -4,6 +4,4 @@ set -e
 
 if [ "$TRAVIS_OS_NAME" = "linux" ]; then
   sudo apt-get install libasound2-dev libjack-jackd2-dev libsndfile1-dev
-elif [ "$TRAVIS_OS_NAME" = "osx" ]; then
-  brew install libsndfile
 fi