Metadata fix for SourceCard, and api upgrade

• The api version supported has been bumped to 09.08.2015
• A bug was fixed when using Metadata with SourceCard (and other nested objects)

API Upgrades, Fraud Details, OAuth Changes, More Managed Accounts

• The supported Stripe API has been bumped to 08.07.2015 (as I've said before, Stripe.net supports a much higher version, it just needs to be verified!)
• Managed Accounts now lets you pass every single option except additional owners (all other legal entity values are present)
• The OAuth endpoint now supports Deauthorize
• There is a class called SubscriptionStatuses you can use to get all available values

Async

• All of the Stripe.net services now support async

Better Debugging and Easier Sources

• StripeSourceOptions has been marked obsolete. Now, you will use either StripeToken (or StripeTokenOrExistingSourceId on charges), or a StripeCard. The readme has been updated.
• The POST data has been moved from the URL to the body for all messages. This helps you debug and get better error messages.
• The version of Stripe.net is now in the User Agent, for better support.

Metadata Fixed and Small Breaking Change

• There was a bug when using Metadata with charges/cards. This has been fixed.
• The supported Stripe api has been bumped up to 2015-07-28 (a lot of newer api changes apply, they have just not been verified).
• Small breaking change: On StripeSubscription, the PeriodStart and PeriodEnd properties have been renamed to CurrentPeriodStart and CurrentPeriodEnd to match Stripe's property names.

Fixes and Optimized Requests

• Fixes for cross platform issues introduced with 6.0.0
• Now uses ModernHttpClient so each platform uses the best optimized http handler
• Upgraded Json.net

Cross Platform

• Stripe.net now supports .NET 4.5+ and is a portable class library. UWP, .NET Core, Windows 8, WindowsPhone 8.0+, and Xamarin are now supported. Many thanks to a great deal of individuals who helped pull this off.
• Bumped the api version to 3.24. (a lot of new api features are already supported)

Managed Accounts

�Managed Accounts support is finally here, mostly. :)

• There are still a few things left to add when creating and updating accounts (Legal Entity, TOS Acceptance, and Transfer Schedules).
• A few of the properties for StripeAccount and it's nested entities have changed, due to finding issues when testing managed accounts

StripeUpcomingInvoiceOptions support, Updating Stripe charge support, small fixes

• Upcoming invoices now supports a StripeUpcomingInvoiceOptions entity (small breaking change)
• DueBy is now nullable on StripeAccountVerification
• Added support for updating Stripe charges in the StripeChargeService

Account Entity Complete

The StripeAccount entity has now been overhauled to support all properties available from Stripe, including all nested objects... FileUpload, StripeLegalEntity, etc. This is the the first iteration of the work necessary to support managed accounts.