Add TravisCI config (#104)

* Add TravisCI config
* Test against Go 1.9+

.travis.yml

@@ -0,0 +1,29 @@
+language: go
+
+os:
+  - linux
+  - osx
+
+go:
+  - 1.9.x
+  - 1.10.x
+  - 1.11.x
+  - 1.12.x
+  - 1.13.x
+  - tip
+
+matrix:
+  allow_failures:
+    - go: tip
+
+before_install:
+  - if [[ $TRAVIS_GO_VERSION == 1.13* ]]; then go get github.com/axw/gocov/gocov github.com/modocache/gover github.com/mattn/goveralls; fi
+
+script:
+  - go test -v -tags ci ./...
+  - if [[ $TRAVIS_GO_VERSION == 1.13* ]]; then $GOPATH/bin/goveralls -service=travis-ci; fi
+
+notifications:
+  email:
+    on_success: change
+    on_failure: always