Great stuff! I honestly find it shameful that they don't have an api. A couple of months ago I built one in Node.js (https://github.com/kenshiro-o/RapGenius-JS).
If anyone is interested in improving/using the project let me know!
As I've said in other comments, I'd love RG to have a public API, but I can see why they don't.
It'd be cool to compare notes on parsing Rap Genius. Drop me an email if you have a moment, me@timrogers.co.uk.