Fix #21: Add links to contributing.md

CONTRIBUTING.md

@@ -1,14 +1,21 @@
 # Web Platform Working Group
 
-Contributions to this repository are intended to become part of Recommendation-track documents governed by the
-[W3C Patent Policy](http://www.w3.org/Consortium/Patent-Policy-20040205/) and
-[Software and Document License](http://www.w3.org/Consortium/Legal/copyright-software). To make substantive contributions to specifications, you must either participate
-in the relevant W3C Working Group or make a non-member patent licensing commitment.
+Contributions to this repository are intended to become part of
+Recommendation-track documents governed by the
+	[W3C Patent Policy](http://www.w3.org/Consortium/Patent-Policy-20040205/)
+and
+	[Software and Document License](http://www.w3.org/Consortium/Legal/copyright-software).
+To make substantive contributions to specifications, you must either participate
+in the W3C
+	[Web Platform Working Group](https://www.w3.org/WebPlatform/WG/)
+or make a
+	[non-member patent licensing commitment](https://www.w3.org/2004/01/pp-impl/83482/nmlc).
 
-If you are not the sole contributor to a contribution (pull request), please identify all 
-contributors in the pull request comment.
+If you are not the sole contributor to a contribution (pull request), please
+identify all contributors in the pull request comment.
 
-To add a contributor (other than yourself, that's automatic), mark them one per line as follows:
+To add a contributor (other than yourself, that's automatic), mark them one per
+line as follows:
 
 ```
 +@github_username
@@ -20,5 +27,5 @@ If you added a contributor by mistake, you can remove them in a comment with:
 -@github_username
 ```
 
-If you are making a pull request on behalf of someone else but you had no part in designing the 
-feature, you can remove yourself with the above syntax.
+If you are making a pull request on behalf of someone else but you had no part
+in designing the feature, you can remove yourself with the above syntax.