Corrected capital H's in 'GitHub' (#3)

The capital H fairy has visited your repo ✨

Thanks for this project folks, just what I was looking for!

Signed-Off-By: Joe Nash <joenash@github.com>

Author: Joe Nash

README.md

@@ -2,9 +2,9 @@
 
 [![PyPI](https://img.shields.io/pypi/v/github-webhook.svg)][2]
 
-`python-github-webhook` is a very simple, but powerful, microframework for writing [Github
+`python-github-webhook` is a very simple, but powerful, microframework for writing [GitHub
 webhooks][1] in Python. It can be used to write webhooks for individual repositories or whole
-organisations, and can be used for Github.com or Github Enterprise installations; in fact, it was
+organisations, and can be used for GitHub.com or GitHub Enterprise installations; in fact, it was
 orginally developed for Bloomberg's GHE install.
 
 ## Getting started