Added examples for using go.stripe with Stripe.js and Stripe Checkout.

Additionally updated comment in charge.go to refer to currently
supported currencies.
Merge pull request #17 from elithrar/master

Added Examples for Stripe.js & Stripe Checkout
Merge pull request #18 from irwinb/master

Update to 2013-08-13 API
Correcting import path
Merge pull request #20 from purohit/patch-1

Correcting import path
Updating docs: s/bradrydzewski/drone
Refactoring errors and adding codes/types provided by Stripe + go fmt
Merge pull request #22 from purohit/master

Updating docs: s/bradrydzewski/drone
Tests for good and bad cards from Stripe
Merge pull request #23 from purohit/errors

Adding error constants, refactoring error struct, and tests
Adding a new param to CustomerParams.  default_card.