Fix visual tests, fail build if vusial tests failing

.gemini.yml

@@ -1,5 +1,5 @@
-rootUrl: http://127.0.0.1:8080/components/vaadin-button/test/visual/
-gridUrl: http://127.0.0.1:4444/wd/hub
+rootUrl: http://localhost:8080/components/vaadin-button/test/visual/
+gridUrl: http://localhost:4444/wd/hub
 screenshotsDir: ./test/visual/screens
 
 system:

.travis.yml

@@ -23,9 +23,9 @@ before_script:
 
 script:
   - if [[ "$TRAVIS_EVENT_TYPE" != "pull_request" && "$TRAVIS_BRANCH" != quick/* ]]; then
-      npm i gemini@^4.0.0 gemini-sauce gemini-polyserve;
-      gemini test test/visual;
-      gemini test test/visual -c .gemini-ie.yml;
+      npm i gemini@^4.0.0 gemini-sauce gemini-polyserve &&
+      gemini test test/visual &&
+      gemini test test/visual -c .gemini-ie.yml &&
       xvfb-run -s '-screen 0 1024x768x24' polymer test --env saucelabs;
     fi
   - if [ "$TRAVIS_EVENT_TYPE" = "cron" ]; then