2.0.0-alpha.6

• Sligtly better error handling
• Allow for stripe_user params to be passed as part of connect URL
• Allow passing api_key to override default one.
• Added ability to update Customer source
• Added ExternalAccount endpoints ([:create, :retrieve, :update, :delete]
• Added FileUpload endpoints ([:create, :retrieve])
• Added Account.create, added some missing fields to Account
• Removed datetime conversions. datetime fields are now unix timestamp integers, as they are in the original Stripe API response. We don't want to impose a format on the user.
• Fixed Customer.update
• Added Invoice endpoints ([:create, :retrieve, :update])
• Added basic support for List objects (step towards :retrieve_all)
• Added :type field to all structs
• Added Charge endpoints ([:create, :retrieve])
• Added Token.create
• Lots of internal improvements, which will hopefully make moving forward easier