Remove CA and link to main contributing

CONTRIBUTING.md

@@ -1 +1 @@
-Like with Clojure and most other big OSS projects, we have a [Contributor's Agreement](https://docs.google.com/a/kodowa.com/forms/d/1ME_PT6qLKUcALUEz1h1yerLF7vP_Rnohpb9RvMLDALg/viewform) that you have to agree to before we can merge. It's a simple adaptation of Twitter's own Contributor's Agreement and just says that by signing this you can't take the code back from us or sue us into oblivion for using it later.
+See [Light Table's CONTRIBUTING.md](https://github.com/LightTable/LightTable/blob/master/CONTRIBUTING.md).