cheatsheet: new sections needed

[oakmac]

The cheatsheet is missing some sections.

• zippers
• abstractions
• reader macros
• core.async

[shaunlebron]

added core.async to the doc generator

[oakmac]

In addition to adding some sections, there are a few missing functions from the cheatsheet that need to be added. I have a list on my desk, copying it here:

• do
• defmacro (which section should this go in?)
• letfn
• quote
• loop
• recur
• not
• identical?
• name

I need to do another pass against the existing cheatsheet and add anything that's missing.