Adding MOIP [brazilian] gateway  (WIP)

Still a work in progress!

## TODO

- [x] Organize code and clean bad code from moip.rb
- [x] Add unit test
- [ ] Add #authorize and #capture method
- [ ] Find out a way to do remote test without hitting MOIP with out hitting MOIP server (VCR, maybe?)
- [ ] Add API to get purchase information