add travis.

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

.travis.yml

@@ -0,0 +1,22 @@
+language: go
+sudo: false
+
+go:
+  - 1.5.4
+  - 1.6.4
+  - 1.7.4
+  - tip
+
+script:
+  - go test -v -covermode=atomic -coverprofile=coverage.out
+
+after_success:
+  - bash <(curl -s https://codecov.io/bash)
+
+notifications:
+  webhooks:
+    urls:
+      - https://webhooks.gitter.im/e/acc2c57482e94b44f557
+    on_success: change
+    on_failure: always
+    on_start: false