Move contributing guidelines to wiki

CONTRIBUTING.md

-# Contribute to DGraph
-
-**Pull requests are welcome.**
-
-## Style Guide
-We're following [Go Code Review](https://github.com/golang/go/wiki/CodeReviewComments).
-Use `gofmt` for formatting your code. Avoid unnecessary vertical spaces.
-Wrap your code and comments to 100 characters, unless doing so makes the code less legible.
-
-## Code Review Workflow
-- All contributors need to sign the [Contributor License Agreement](https://cla-assistant.io/dgraph-io/dgraph).
-- Pick an issue from [pending issues](https://github.com/dgraph-io/dgraph/issues).
-- If the issue isn't currently present in the list, file a new issue,
-or bring it up on [Google Group](https://groups.google.com/forum/#!forum/dgraph) or [Gitter Chat](https://gitter.im/dgraph-io/dgraph),
-so someone can file an issue on your behalf.
-- Indicate that you're working on the issue by assigning the issue to yourself.
-- Create a new branch, write your code, and commit your changes locally.
-- Make sure you run `go test ./...` from the root.
-- [Create a pull request](https://help.github.com/articles/creating-a-pull-request/)
-- DGraph uses [Reviewable](https://reviewable.io/) for code reviews, and follows a rigorous code review process.
-- Address the comments, and repeat the cycle, until you get an LGTM by someone qualified.
-- Once you have an LGTM, go ahead and merge.
-Most new contributors aren't allowed to merge themselves, in that case, we'll do it for you.

README.md

@@ -201,6 +201,9 @@ Consecutive runs of the same query took much lesser time (100ms), due to posting
 }
 ```
 
+# Contributing to DGraph
+- Please see [this wiki page](https://github.com/dgraph-io/dgraph/wiki/Contributing-to-DGraph) for guidelines on contributions.
+
 # Contact
 - Check out [the wiki pages](https://github.com/dgraph-io/dgraph/wiki) for documentation.
 - Please use [Github issue tracker](https://github.com/dgraph-io/dgraph/issues) to file bugs, or request features.