surround travis PATH in quotes

Author: bshaffer

.travis.yml

@@ -31,7 +31,7 @@ env:
   global:
     - GOOGLE_APPLICATION_CREDENTIALS=$TRAVIS_BUILD_DIR/credentials.json
     - GOOGLE_VERSION_ID=$TRAVIS_JOB_ID
-    - PATH=${HOME}/google-cloud-sdk/bin:${PATH}
+    - PATH="${HOME}/google-cloud-sdk/bin:${PATH}"
     - PHP_CGI_PATH=/home/travis/.phpenv/shims/php-cgi
     - TEST_BUILD_DIR=$TRAVIS_BUILD_DIR