async highlighter support. closes #47.
allow dashes in language names. fixes #138.
Revert "allow dashes in language names. fixes #138."

This reverts commit 608fdb3a1b35ce9da6461ea2e9b15a22909aa447.
add preliminary smartypants code. see #137.
add smartypants test.
do not escape script elements. fixes #142.

this is not accurate to the original markdown.pl,
but neither is not escaping `<pre>` elements.
implement smartypants.
Revert "implement smartypants."

This reverts commit d1990428bcfb1ab9da3a87f9e7024abbce732a90.