Do not check Go version user is building with
Do not check Go version user is building with

This was I guess to stop builds pre Go 1.7 but that is very old
now, and the check breaks on every new Go release. I think we
can just document any requirements instead.

Signed-off-by: Justin Cormack <af64ee19f04db9509cb02b0e470e11e5402ef9b3@docker.com>

HuKeping/notary,docker/notary,docker/notary,docker/notary,jfrazelle/notary,jfrazelle/notary,HuKeping/notary,HuKeping/notary,jfrazelle/notary