build: add ci config

Author: Yifeng Wang

.travis.yml

@@ -0,0 +1,15 @@
+language: node_js
+node_js:
+- stable
+cache:
+  yarn: true
+
+env:
+  # Do two runs, one for testing and one for linting.
+  matrix:
+    - TEST_TYPE=lint
+    - TEST_TYPE=test
+
+script:
+  # Run testing or linting depending on the environment.
+  - yarn run $TEST_TYPE