Update go dependencies (#2234)

vendor/github.com/gregjones/httpcache/.travis.yml

@@ -1,19 +0,0 @@
-sudo: false
-language: go
-go:
-  - 1.6.x
-  - 1.7.x
-  - 1.8.x
-  - 1.9.x
-  - master
-matrix:
-  allow_failures:
-    - go: master
-  fast_finish: true
-install:
-  - # Do nothing. This is needed to prevent default install action "go get -t -v ./..." from happening here (we want it to happen inside script step).
-script:
-  - go get -t -v ./...
-  - diff -u <(echo -n) <(gofmt -d .)
-  - go tool vet .
-  - go test -v -race ./...