-------------------
* 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