Bitarray

-------------------
* add `.clear()` method (Python 3.3 added this method to lists)
* avoid over-allocation when bitarray objects are initially created
* raise BufferError when resizing bitarrays which is exporting buffers
* add example to study the resize() function
* improve some error messages
* add more tests
* raise `NotImplementedError` with (useful message) when trying to call
the `.fromstring()` or `.tostring()` methods, which have been removed
in the last release

-------------------
* add `bitarray.util.make_endian()`
* `util.ba2hex()` and `util.hex2ba()` now also support little-endian
* add `bitarray.get_default_endian()`
* made first argument of initializer a positional-only parameter
* remove `.fromstring()` and `.tostring()` methods, these have been
deprecated 8 years ago, since version 0.4.0
* add `__all__` in `bitarray/__init__.py`
* drop Python 3.3 and 3.4 support

-------------------
* `util.ba2hex()` now always return a string object (instead of bytes
object for Python 3), see issue 94
* `util.hex2ba` allows a unicode object as input on Python 2
* Determine 64-bitness of interpreter in a cross-platform fashion 91,
in order to better support PyPy

-------------------
* simplify markdown of readme so PyPI renders better
* make tests for bitarray.util required (instead of warning when
they cannot be imported)

-------------------
* add bitarray.util module which provides useful utility functions
* deprecate `bitarray.bitdiff()` in favor of `bitarray.util.count_xor()`
* use markdown for documentation
* fix bug in `.count()` on 32bit systems in special cases when array size
is 2^29 bits or larger
* simplified tests by using bytes syntax
* update smallints and sieve example to use new utility module
* simplified mandel example to use numba
* use file context managers in tests

-------------------
* add frozenbitarray object
* add optional start and stop arguments to `.count()` method
* add official Python 3.8 support
* optimize `setrange()` (C-function) by using `memset()`
* fix issue 74, bitarray is hashable on Python 2
* fix issue 68, `unittest.TestCase.assert_` deprecated
* improved test suite - tests should run in about 1 second
* update documentation to use positional-only syntax in docstrings
* update readme to pass Python 3 doctest
* add utils module to examples