disable homebrew autoupdate during pyenv-virtualenv because it causes timeout due to the long time that a homebrew update takes.

Author: rafaelcapucho

Diff for: .travis.yml

@@ -61,6 +61,7 @@ branches:
 before_install: |
     if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then
       # From https://pythonhosted.org/CodeChat/.travis.yml.html
+      export HOMEBREW_NO_AUTO_UPDATE=1
       brew install pyenv-virtualenv
       eval "$(pyenv init -)"
       eval "$(pyenv virtualenv-init -)"