Make golint fail the build

Very weird program behavior

Signed-off-by: Vadim Markovtsev <vadim@sourced.tech>

.travis.yml

@@ -47,7 +47,7 @@ install:
   - make
 script:
   - go vet ./...
-  - golint ./...
+  - golint -set_exit_status ./...
   - go test -v -cpu=1,2 -coverprofile=coverage.txt -covermode=count gopkg.in/src-d/hercules.v3
   - $GOPATH/bin/hercules version
   - $GOPATH/bin/hercules --burndown --couples --quiet --pb https://github.com/src-d/hercules > 1.pb