Use mod vendor for vendored directory (backwards compatible)

vendor/github.com/valyala/bytebufferpool/.travis.yml

@@ -0,0 +1,15 @@
+language: go
+
+go:
+  - 1.6
+
+script:
+  # build test for supported platforms
+  - GOOS=linux go build
+  - GOOS=darwin go build
+  - GOOS=freebsd go build
+  - GOOS=windows go build
+  - GOARCH=386 go build
+
+  # run tests on a standard platform
+  - go test -v ./...