Fix travis to only difftest on go 1.9
Fix travis to only difftest on go 1.9

Go master contains the commit hash that it was built at (or some similar
token). Unfortunately our regexp that we were checking against had an
escaping error. `grep -q 1.9` instead of `grep -q 1\.9` which meant it
was matching 1[any character]2. The current golang master commit is

"go version devel +15bc0a129a Wed Jan 3 04:34:11 2018 +0000 linux/amd64"

Fixes by making the string A LOT more specific and escaping.

grpc-ecosystem/grpc-gateway,ilius/grpc-gateway,ilius/grpc-gateway,gengo/grpc-gateway,improbable-io/grpc-gateway,improbable-io/grpc-gateway,ilius/grpc-gateway,gengo/grpc-gateway