simplify stuff

this removes almost everything, including the `xmlhttprequest` polyfill. I couldn't make heads or tails of the previous build system (required ruby and makefiles).

this adds browserling tests, and will make it a lot easier to contribute to this repo. we'll need to add back a cross browser xhr polyfill, but it can be done in a sane way with tests this time.

at this time iriscouch/browser-request doesn't work in FF but this one does