v4.0.0 Initial async release

Initial release of a new fork of the benjaminfavre/oauth2-http-client library that handles OAuth 2 authentication to the symfony/http-client. This fork changes the operating mode of the client decorator to be asynchronous.

General Features

• Asynchronous symfony/http-client decorator
• Implements most standard OAuth 2 grant types. Easily extensible.
• Use standalone or in a full framework application
• Minor fixes/enhancements (see README with summary of changes from upstream)

Full Changelog: https://github.com/hfig/oauth2-http-client/commits/v4.0.0