docs could use more examples

[kurtbrose]

As I was learning parsley, I made a bunch of little notes / idioms for doing things:

https://gist.github.com/kurtbrose/05f2dd879eba6a88a3dc7c13e36ce772

There are also some larger grammars I defined:

TLS RFC parsing:
https://gist.github.com/kurtbrose/bb98bdf42dc709cbc5a1b94b058b703c

Thrift IDL Parsing:
https://github.com/kurtbrose/thriftpy/blob/new_parser/thriftpy/parser/parser.py#L395-L497