CONTRIBUTING.md: Capitalize "GitHub" the way GitHub does

Fixes #200

MOE_MIGRATED_REVID=170552533

Author: apjanke

CONTRIBUTING.md

@@ -1,8 +1,11 @@
-Want to contribute? Great! First, read this page (including the small print at the end).
+Want to contribute? Great! First, read this page (including the small print at
+the end).
 
 ### Before you contribute
-Before we can use your code, you must sign the
-[Google Individual Contributor License Agreement](https://developers.google.com/open-source/cla/individual?csw=1)
+
+Before we can use your code, you must sign the [Google Individual Contributor
+License
+Agreement](https://developers.google.com/open-source/cla/individual?csw=1)
 (CLA), which you can do online. The CLA is necessary mainly because you own the
 copyright to your changes, even after your contribution becomes part of our
 codebase, so we need your permission to use and distribute your code. We also
@@ -16,9 +19,11 @@ possibly guide you. Coordinating up front makes it much easier to avoid
 frustration later on.
 
 ### Code reviews
+
 All submissions, including submissions by project members, require review. We
-use Github pull requests for this purpose.
+use GitHub pull requests for this purpose.
 
 ### The small print
-Contributions made by corporations are covered by a different agreement than
-the one above, the Software Grant and Corporate Contributor License Agreement.
+
+Contributions made by corporations are covered by a different agreement than the
+one above, the Software Grant and Corporate Contributor License Agreement.