Check for old golang versions while installing dependencies.

misc/make-deps.sh

@@ -32,6 +32,12 @@ if [ $travis -eq 0 ]; then
 	fi
 fi
 
+# if golang is too old, we don't want to fail with an obscure error later
+if go version | grep 'go1\.[0123]\.'; then
+	echo "mgmt requires go1.4 or higher."
+	exit 1
+fi
+
 go get ./...	# get all the go dependencies
 [ -e "$GOBIN/mgmt" ] && rm -f "$GOBIN/mgmt"	# the `go get` version has no -X
 # vet is built-in in go 1.6 - we check for go vet command