added groupings by markdown headings

[mynameisfiber]

#4 wanted groupings by different types of events (and so do I!). This code allows you to group things by using markdown headers.

I would like to add some more stylistic things (have the headers be fixed for x-scroll but scroll for y-scroll) and some stylistic things, but I'm not quite sure how to do that without adding jquery as a dependency (which I don't want to do!).

[popomore]

Great!

[justinthiele]

Excited for this one to get merged in.

[mynameisfiber]

@cheeaun sorry for the delay! I think my modifications are done... what do you think?

[clawoflight]

@cheeaun Any news on this? I would love to have it!