Travis: replace homebrew/versions/qt55 with qt5

.travis/osx..install.sh

@@ -3,7 +3,7 @@
 PACKAGES="cmake pkgconfig fftw libogg libvorbis lame libsndfile libsamplerate jack sdl libgig libsoundio stk portaudio node fltk"
 
 if [ $QT5 ]; then
-	PACKAGES="$PACKAGES homebrew/versions/qt55"
+	PACKAGES="$PACKAGES qt5"
 else
 	PACKAGES="$PACKAGES cartr/qt4/qt"
 fi

.travis/osx..script.sh

@@ -2,7 +2,7 @@
 
 if [ $QT5 ]; then
         # Workaround; No FindQt5.cmake module exists
-        export CMAKE_PREFIX_PATH="$(brew --prefix qt55)"
+        export CMAKE_PREFIX_PATH="$(brew --prefix qt5)"
 fi
 
 cmake $CMAKE_FLAGS -DUSE_WERROR=OFF ..