better examples

[ylixir]

update the examples to include easy, medium and advanced examples.

easy should be an example of parsing some regular grammar. maybe a wordpress shortcode.

medium should be some context free grammar. maybe like a json parser or something.

advanced should show advanced processing and multiple layers of parsers. something like a lisp interpreter. rip off mary cooks javascript lisp interpreter?

we should also include a page for each on the site explaining these things

• easy code
• easy docs and tests
• medium code
• medium docs and tests
• advanced code
• advanced docs and tests