rename `go` to `golang` to fix issue with creating binary called `go`

Previously, if you were to do something like `go get -t -u -v github.com/cloudfoundry/cf-acceptance-test/...` then you'd end up creating a binary called `go` which would end up in `$GOPATH/bin`.  Depending on where that was on your `$PATH`, the `go` command would no longer be the thing to manage and build Golang code, it would instead start a little web server and you'd just see the output `listening ...`, or potentially a runtime panic if the server tries to start listening on a tcp connection with no `$PORT` specified.