Add a threshold based golint test case

This lets some golint errors in, but fails if you're over a certain
threshold. The current threshold of 15% (of LOC) is arbitrary and
subject to change. The algorithm should be extended to check a range of
commits, although it's unclear how to detect what range of commits make
up a patch set.

misc/make-deps.sh

@@ -41,3 +41,4 @@ go get ./...	# get all the go dependencies
 [ -e "$GOBIN/mgmt" ] && rm -f "$GOBIN/mgmt"	# the `go get` version has no -X
 go get golang.org/x/tools/cmd/vet	# add in `go vet` for travis
 go get golang.org/x/tools/cmd/stringer	# for automatic stringer-ing
+go get github.com/golang/lint/golint	# for `golint`-ing