Merge pull request #3769 from msoap/fix-docs

documentation: changed link to style doc
LGTM. Link accurate (old link was redir'd anyway).
Tiny fix, doc-only, so directly merging.

CONTRIBUTING.md

@@ -35,7 +35,7 @@ Thanks for your contributions!
 
 ### Code style
 
-The coding style suggested by the Golang community is used in etcd. See the [style doc](https://code.google.com/p/go-wiki/wiki/CodeReviewComments) for details.
+The coding style suggested by the Golang community is used in etcd. See the [style doc](https://github.com/golang/go/wiki/CodeReviewComments) for details.
 
 Please follow this style to make etcd easy to review, maintain and develop.