I had assumed a relative link to another markdown file in this project
would work, but it renders as:
http://learnxinyminutes.com/docs/hack/php.html.markdown
instead of the desired:
http://learnxinyminutes.com/docs/php/
I've replaced this relative link with an absolute link to where the target
page is located on the published site.
This commit also fixes a typo in markdown syntax at the end of the document.