Cbor2

- Fix segfault when initializing CBORTag with incorrect arguments (Sekenre)
- Fix sphinx build warnings (Sekenre)

- Fix SystemErrors when using C-backend, meaningful exceptions now raised (Sekenre)
- Fix precision loss when decoding base10 decimal fractions (Sekenre)
- Made CBORTag handling consistent between python and C-module (Sekenre)

- Fix various bounds checks in the C-backend (Sekenre)
- More testing of invalid/corrupted data (Sekenre)
- Support for `String References <http://cbor.schmorp.de/stringref>`_ (xurtis)
- Update Docs to refer to new RFC8949

- Removed support for Python < 3.6

- Final version tested with Python 2.7 and 3.5
- README: Announce deprecation of Python 2.7, 3.5
- README: More detail and examples
- Bugfix: Fix segfault on loading huge arrays with C-backend (Sekenre)
- Build system: Allow packagers to force C-backend building or disable using env var (jameshilliard)
- Feature: ``cbor2.tool`` Command line diagnostic tool (Sekenre)
- Feature: Ignore semantic tag used for file magic 55799 AKA "Self-Described CBOR" (kalcutter)

- Bugfix: Refcount bug in C lib causing intermittent segfaults on shutdown (tdryer)