travis: improve travis config

.travis.yml

@@ -1,9 +1,21 @@
 language: go
 
+go:
+  - 1.7.5
+  - 1.8.3
+  - 1.9
+  - tip
+
 matrix:
-  include:
-    - go: 1.6.3
-    - go: 1.7.5
-    - go: 1.8.2
-    - go: 1.9
-    - go: master
+  allow_failures:
+    - go: tip
+  fast_finish: true
+
+before_script:
+  - GO_FILES=$(find . -iname '*.go' | grep -v /vendor/)
+  - PKGS=$(go list ./... | grep -v /vendor/)
+
+script:
+  - test -z $(gofmt -s -l $GO_FILES)
+  - go test -v -race $PKGS
+  - go vet $PKGS