Change all the emphasis "headings" to headings

By using headings for each section under the intro instead of emphasis
tags, GitHub exposes anchors that make each section linkable.
Unfortunately headings need to be on one line.
Merge pull request #28 from amaltson/readme-anchors

Change all the emphasis "headings" to headings
Pass options to #defer
Move definition of conversion functions out of module initializer.
Remove unused variable
Merge pull request #30 from padi/remove-unused-variable

Remove unused variable