Possible ways to build a document-previewer utility (so you don't have to check them in a hundred times, just to make one small change, and spam the commit history):

• use Github's Markdown Rendering API
  • already done:
    • TextMate plugin
    • Sublime 2 plugin
    • others: [1] [2] [3]
• use gist.github.com
  • it renders markdown, presumably JUST like github itself
  • you can make a specific gist private, if you want, since it's usually of little use to others
  • unfortunately, these formats aren't supported there: README.creole
  • see the start of some possible code here