Merge pull request #52 from xoviat/osx

MRG: OSX: never update homebrew

Workaround for travis-ci/travis-ci#8552 .  Also see 
https://github.com/fonttools/fonttools/issues/1068

osx_utils.sh

@@ -285,6 +285,7 @@ function get_macpython_environment {
     remove_travis_ve_pip
     install_macpython $version
     install_pip
+    export HOMEBREW_NO_AUTO_UPDATE=1
     if [ -n "$venv_dir" ]; then
         install_virtualenv
         make_workon_venv $venv_dir