fix HRs in list items + code. fixes #91.
fix link defs after blocks. nearly fixes #77.
Merge branch 'def_hr_fixes'

Conflicts:
	lib/marked.js
add doc/ and some documentation of markdown inconsistencies.
fix doc formatting.
fix regression caused by merge conflict.
fix double gfm autolinks. fixes #56.
rough implementation of task lists. see #107 #111.
use renderer for task lists. see #107 #111.
Automatically rewritten for npm.