Merge pull request #2 from eaigner/master

Rewrote package, partially implemented subscriptions. Fixes #1.
Merge pull request #3 from eaigner/master

fix braintree configuration in readme
Add some more stuff to the README
Add expiration month and year as fields to credit card
Add sample application
Tweak to comments on test server
Tweak copy of README
customer update api
card number is string
copy object so that field sanitation doesn't affect original; doc comments
sublime text project file for fast project switching
customer delete
don't create struct twice
helper method to get default payment token from customer
make braintree and invalid response error interface types to make type-switching easier. otherwise we would have to distinguish between structs and struct pointers.
implement transaction submit for settlement
void transactions
close response body after error check to avoid nil pointer dereference
Add braintree.sublime-project to gitignore
pass pointer of copied object