Add travis config

Set up travis to test chrome and linux always, and all of our supported browsers
for first-party PRs.

.travis.yml

@@ -0,0 +1,30 @@
+language: node_js
+sudo: false
+cache:
+  directories:
+  - node_modules
+matrix:
+  include:
+  - node_js: stable
+    script: xvfb-run -a wct --simpleOutput -l firefox -l chrome
+    addons:
+      firefox: latest
+      apt:
+        sources:
+        - google-chrome
+        packages:
+        - google-chrome-stable
+  - node_js: node
+    script:
+    - |
+      if [ "${TRAVIS_PULL_REQUEST}" = "false" ]; then
+        wct --simpleOutput -s 'Windows 10/microsoftedge' -s 'Windows 8.1/internet explorer@11' -s 'Windows 7/internet explorer@10' -s 'OS X 10.10/safari@8' -s 'OS X 10.9/safari@7'
+      fi
+before_script:
+- npm install bower web-component-tester
+- export PATH=$PWD/node_modules/.bin:$PATH
+- bower install
+env:
+  global:
+  - secure: eFrp9xwSYG579rAR9/XyXYKh+UtIQJ1xS5q5PABu4ndYFckdJb8o3m7oXqRSikbiPWbCSd3Fkd6+ZKXlcQFdjJ+nx9gFitGthtH93qkvZCO3XhWEEBPj65igIo3hrRSOB6dIWyiZcnoH9IXLLQtKXY9uL1NCqCcyVHg1omPKr9w=
+  - secure: EAjjkzqZ8z+PEvdo2N2MiIjkqUYAjVkQABKyMw6N4hUa6YSNEW9PYyn4I0d9Rdvc25GwJ+oLQFdeQepioAkNfp6wYUj2IdMIfmmKa1aJWo5DWvOMDYp3ufRhIoiVi4ZVpLg9sTjw+078UhUQFWE44rwfUtHiIb2UbWe2/ueLOiM=