Travis Configuration (#4)

Add Travis configuration so tests run on each PR.

Author: kristoferbaxter

.gitignore

@@ -1,5 +1,4 @@
 node_modules/*
-yarn.lock
 yarn-error.log
 .vscode/*
 .DS_Store

.travis.yml

@@ -0,0 +1,15 @@
+language: node_js
+sudo: required  # See http://docs.travis-ci.com/user/trusty-ci-environment/
+dist: trusty
+node_js:
+  - "lts/*"
+before_install:
+  - unset _JAVA_OPTIONS  # JVM heap sizes break closure compiler. #11203.
+script: yarn test
+branches:
+  only:
+    - master
+cache:
+  yarn: true
+  directories:
+    - node_modules