Cbor2

- Build system: Making C lib optional if it fails to compile (chiefnoah)
- Build system: Better Glibc version detection (Sekenre and JayH5)
- Tests: Positive and negative bignums (kalcutter)
- Bugfix: Fractional seconds parsing in datetimes (kalcutter)

- Minor API change: ``CBORSimpleValue`` is now a subclass of namedtuple and allows
all numeric comparisons. This brings functional parity between C and Python modules.
- Fixes for C-module on big-endian systems including floating point decoding, smallint encoding,
and boolean argument handling. Tested on s390x and MIPS32.
- Increase version requred of setuptools during install due to unicode errors.

- Fix deprecation warning on python 3.7, 3.8 (mariano54)
- Minor documentation tweaks

- **BACKWARD INCOMPATIBLE** CBOR does not have a bare DATE type, encoding dates as datetimes
is disabled by default (PR by Changaco)
- **BACKWARD INCOMPATIBLE** ``CBORDecoder.set_shareable()`` only takes the instance to share, not
the shareable's index
- **BACKWARD INCOMPATIBLE** ``CBORError`` now descends from ``Exception`` rather than
``ValueError``; however, subordinate exceptions now descend from ``ValueError`` (where
appropriate) so most users should notice no difference
- **BACKWARD INCOMPATIBLE** ``CBORDecoder`` can now raise ``CBORDecodeEOF`` which inherits
from ``EOFError`` supporting streaming applications
- Optional Pure C implementation by waveform80 that functions identically to the pure Python
implementation with further contributions from: toravir, jonashoechst, Changaco
- Drop Python 3.3 and 3.4 support from the build process; they should still work if built from
source but are no longer officially supported
- Added support for encoding and decoding ``ipaddress.IPv4Address``,
``ipaddress.IPv6Address``, ``ipaddress.IPv4Network``, and ``ipaddress.IPv6Network``
(semantic tags 260 and 261)

- **BROKEN BUILD** Removed

- Fixed bigint encoding taking quadratic time
- Fixed overflow errors when encoding floating point numbers in canonical mode
- Improved decoder performance for dictionaries
- Minor documentation tweaks