Feature/multi example

HI, Great project.

I use styledown to build UI document for my team recently. It looks like the .md .js file is not supported. Multi examples in one section is also not supported. I send this pull request is not for fix it completely, but only show you my idea. I will really happy if this pull request can help you in finishing the job.  

Though it is work well for my document project ( delai.me/kui ). But there is some issue in this pull request:
the example can not be built in the new code, because of keyword like @example.wide. 

I'm really a node newbie, sorry for having not do the job completely. Hope you can fix it.