Benchmark draft subdirs

you can now do this:

`coffee benchmarks/draft3/medium`

or this:

`coffee benchmarks/draft4/trivial`

or `draft3/trivial`, or `draft4/medium`. and directories named `draft3/complex` and `draft4/complex` eagerly await appropriate schemae and docs.

`#TODO`: unfortunately the code's a bit repetitive, and no `index.coffee` files yet exist for the `draft{3,4}` folders.