pure-Python implementation of the HTTP/2 priority tree (Python 3)

 Priority is a pure-Python implementation of the priority logic for HTTP/2, set
 out in RFC 7540 Section 5.3 (Stream Priority). This logic allows for clients
 to express a preference for how the server allocates its (limited) resources to
 the many outstanding HTTP requests that may be running over a single HTTP/2
 connection.
 .
 Specifically, this Python implementation uses a variant of the implementation
 used in the H2O project. This original implementation is also the
 inspiration for nghttp2's priority implementation, and generally produces a
 very clean and even priority stream. The only notable changes from H2O's
 implementation are small modifications to allow the priority implementation to
 work cleanly as a separate implementation, rather than being embedded in a
 HTTP/2 stack directly.
 .
 While priority information in HTTP/2 is only a suggestion, rather than an
 enforceable constraint, where possible servers should respect the priority
 requests of their clients.
 .
 This package is for Python 3.