README: Added link to Gittip.

readme.md

@@ -4,6 +4,8 @@ Pretty diff generates colorized HTML diffs similar to the diff/commit views on G
 Simply use `pretty-diff` the same way you use `git diff` and you'll get pretty diffs.
 If you want to share the diff, you can use `gist-diff` and you'll get a new gist.
 
+Support this project by [donating on Gittip](https://www.gittip.com/scottgonzalez/).
+
 ## Installation
 
 Simply install globally via npm:
@@ -38,3 +40,7 @@ However, if you enter an incorrect password, then no gist will be generated.
 ## License
 
 Copyright 2013 Scott González. Released under the terms of the MIT license.
+
+---
+
+Support this project by [donating on Gittip](https://www.gittip.com/scottgonzalez/).