Add a note about required Go version
See https://github.com/McKael/madonctl/issues/1
--- a/README.md Sat Apr 22 14:49:19 2017 +0200
+++ b/README.md Sun Apr 23 15:39:51 2017 +0200
@@ -15,7 +15,7 @@
## Installation
-To install the library:
+To install the library (Go >= v1.5 required):
go get github.com/McKael/madon