get test dependencies too

Author: jeevatkm

.travis.yml

@@ -18,7 +18,7 @@ before_install:
   - go get golang.org/x/tools/cmd/cover
 
 install:
-  - go get -v ./...
+  - go get -v -t ./...
 
 script:
   - go test -v ./... -coverprofile=coverage.txt -covermode=atomic