Fixed #216. WikiLink Extension actually accepts configs.
AbbrExtension now handles abbreviations nested in other markup.

Just set each abreviation as an AtomicString. Given the nature of
abbreviations, they are not likely to ever contain any other markup
anyway. Also added a test.

Fixes #224. Thanks for the report @JakeChampion.
Improved codehilite docs. Document `css_class` setting.

Also cleaned up poor wording on other setting for codehilite.

Thanks for the inital suggestion @davidcorne. Fixes #223.
Fixed wikilinks extension's handling of config setting. Not sure how I didn't notice the tests were failing for this before.
Attr_List Extension now support attr_lists on nested lists.

A list item with a nested list complicates were the attr_list can be.

Fixes #218. Thanks for the report @jpzimmer.
Minor cleanup.
MetaData no longer fails with no newline. Fixes #228.
Attr_List Extension now also supports nested ol's.

Not sure how I missed that when committing ea4af0d. Also as a side-effect,
this fixes #230 - which brought my previous oversight to my attention.
Thanks for the report @divisoryang.

Also added some tests - including tests of list items without attr_lists.
Sometimes I forget to test markup that does not use an extension when an
extension is enabled. That's what resulted in #230 being reported.
Allow inline attr_lists at end of header.

A header can be only one line - so unlike other block level elements, a
attr_list must be at th eend of the line. To disingush it from an inline
attr_list on the last child in a header, we must require at least one
space before th eblock-level attrt_list.

Always intended it to work that way. Not sure how I missed that before.
At least we're testing for it now.
Added support for attr_lists on definition list terms.

Like headers (h1-6) dt's can only be on one line, so we need to use
the header regex on dt's. This was implemented after considering a recent
[discussion](http://six.pairlist.net/pipermail/markdown-discuss/2013-July/002859.html)
on the markdown mailing list. Prior to that discussion, I never considered
that it was impossable to set block level attrs on dt's. Now it is.
Add smarty extension, based on SmartyPants library