Add mention of Parker Moore (@parkr) in README.

By now, I have almost entirely rewritten Jekyll with the help of our awesome
contributors. Taking a look at the contributions graphs GitHub provides,
I have to date pushed 1,452 commits to master with 24,991 additions and
17,330 deletions. In contrast, Tom Preston-Werner has pushed 295 commits
and 13,461 additions and 6,806 deletions. I don't need to have my name all
over it, but I think I have worked hard enough over the last 21 months
to deserve to put my name alongside Tom's and Nick's.

The lovely thing about version control is that changes can always be reverted.

Thanks for launching this great product, @mojombo and @qrush. I hope I haven't
let you down.

README.markdown

@@ -5,7 +5,7 @@
 [![Code Climate](http://img.shields.io/codeclimate/github/jekyll/jekyll.svg)](https://codeclimate.com/github/jekyll/jekyll)
 [![Dependency Status](https://gemnasium.com/jekyll/jekyll.svg)](https://gemnasium.com/jekyll/jekyll)
 
-By Tom Preston-Werner, Nick Quaranto, and many [awesome contributors](https://github.com/jekyll/jekyll/graphs/contributors)!
+By Tom Preston-Werner, Nick Quaranto, Parker Moore, and many [awesome contributors](https://github.com/jekyll/jekyll/graphs/contributors)!
 
 Jekyll is a simple, blog-aware, static site generator perfect for personal, project, or organization sites. Think of it like a file-based CMS, without all the complexity. Jekyll takes your content, renders Markdown and Liquid templates, and spits out a complete, static website ready to be served by Apache, Nginx or another web server. Jekyll is the engine behind [GitHub Pages](http://pages.github.com), which you can use to host sites right from your GitHub repositories.