add gitter badge

add gitter badge & remove codewake as nobody used anyway

Author: Dean Karn

README.md

@@ -7,7 +7,7 @@ Package form
 [![Go Report Card](https://goreportcard.com/badge/github.com/go-playground/form)](https://goreportcard.com/report/github.com/go-playground/form)
 [![GoDoc](https://godoc.org/github.com/go-playground/form?status.svg)](https://godoc.org/github.com/go-playground/form)
 ![License](https://img.shields.io/dub/l/vibe-d.svg)
-[![Codewake](https://www.codewake.com/badges/codewake2.svg)](https://www.codewake.com/p/form)
+[![Gitter](https://badges.gitter.im/go-playground/form.svg)](https://gitter.im/go-playground/form?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
 
 Package form Decodes url.Values into Go value(s) and Encodes Go value(s) into url.Values.