Fix display of triple-backtick to be cross-renderer

GitHub Flavored Markdown (where this README.md is rendered) was showing the triple tick as <code> </code>\`<code> </code>.

This fixes it to correctly display 3 backtick characters when rendered.

Tested in reference implementation, Github, and dillinger.io
Merge pull request #205 from jesstelford/patch-1

Fix display of triple-backtick to be cross-renderer