chore(travis): do not use npm cache in travis config

This reverts commit e14d1a7.

Author: btford

.travis.yml

@@ -21,7 +21,6 @@ env:
 before_script:
   - mkdir -p $LOGS_DIR
   - ./lib/sauce/sauce_connect_setup.sh
-  - npm config set registry http://23.251.144.68
   - npm install -g grunt-cli
   - grunt package
   - ./scripts/travis/wait_for_browser_provider.sh