Update pycryptodome to 3.7.0

[pyup-bot]

This PR updates pycryptodome from 3.6.6 to 3.7.0.

Changelog

3.7.0

+++++++++++++++++++++++

New features
------------

* Added support for Poly1305 MAC (with AES and ChaCha20 ciphers for key derivation).
* Added support for ChaCha20-Poly1305 AEAD cipher.
* New parameter ``output`` for ``Crypto.Util.strxor.strxor``, ``Crypto.Util.strxor.strxor_c``,
``encrypt`` and ``decrypt`` methods in symmetric ciphers (``Crypto.Cipher`` package).
``output`` is a pre-allocated buffer (a ``bytearray`` or a writeable ``memoryview``)
where the result must be stored.
This requires less memory for very large payloads; it is also more efficient when
encrypting (or decrypting) several small payloads.

Resolved issues
---------------

* GH266: AES-GCM hangs when processing more than 4GB at a time on x86 with PCLMULQDQ instruction.

Breaks in compatibility
-----------------------

* Drop support for Python 3.3.
* Remove ``Crypto.Util.py3compat.unhexlify`` and ``Crypto.Util.py3compat.hexlify``.
* With the old Python 2.6, use only ``ctypes`` (and not ``cffi``) to interface to native code.

Links

• PyPI: https://pypi.org/project/pycryptodome
• Changelog: https://pyup.io/changelogs/pycryptodome/
• Homepage: https://www.pycryptodome.org

[coveralls]

Coverage remained the same at 96.457% when pulling a3cb80b on pyup-update-pycryptodome-3.6.6-to-3.7.0 into c18276e on master.