remove extraneous 'npm install' from Travis build

.travis.yml

@@ -19,13 +19,11 @@ before_install:
   - export CHROME_BIN=chromium-browser
   - export DISPLAY=:99.0
   - sh -e /etc/init.d/xvfb start
-
-before_script:
-- cd $TEST_DIR # switch to the directory we're testing
-- npm install
+  - cd $TEST_DIR # switch to the directory we're testing
+  # npm install happens here
 
 script:
 - npm run test-ci
 
 after_success:
-  - ./node_modules/.bin/codecov # Send coverage
+  - ./node_modules/.bin/codecov # Send coverage