Update .travis.yml

.travis.yml

@@ -1,12 +1,17 @@
 language: go
 sudo: false
 go:
-  - 1.4
-  - 1.5.4
   - 1.6.4
   - 1.7.4
   - tip
 
+git:
+  depth: 3
+
+install:
+  - go get -v github.com/kardianos/govendor
+  - govendor sync
+
 script:
   - go test -v -covermode=count -coverprofile=coverage.out