Updated markdown README URL.

Author: Sanders Kleinfeld

samples/markdown/README.md

@@ -1,4 +1,4 @@
 This directory contains a sample Markdown document (`open_government_sample.md`) 
 and how the corresponding content should be converted to HTMLBook (`open_government_sample.html`).
 
-See oreillymedia/htmlbook.js for open source tooling for converting Markdown to HTMLBook.
+See https://github.com/oreillymedia/htmlbook.js for open source tooling for converting Markdown to HTMLBook.