Try an if statement instead of short-circuited boolean

Author: cthrax

.travis.yml

@@ -9,7 +9,7 @@ os:
 
 script: npm run-script test
 before_install:
-  - $TRAVIS_OS_NAME == "osx" && brew update && brew install nvm
+  - if [[ $TRAVIS_OS_NAME == "osx" ]]; then; brew update; brew install nvm; fi;
   - nvm install $NODE_VERSION
   - npm config set spin false
 install: