Support for PHP 8

Version 2

added auth cache interface

Added more API methods

Added B2 copy support

Stream download capability and added constants

Re-namespaced version before significant code changes.

Added delete and filelist examples (cwhite92#11)

Added delete and list file methods to the example section of the readme

Rename authorise => authorize (#7)

While the spelling is interchangable outside of North America, the B2 API
uses authorize, so we should keep the same spelling here to minimize
confusion.

Fixes #6