Neocore

------------------
* Bugfix: Dont unhex when writing var bytes (`PR 36 <https://github.com/CityOfZion/neo-python-core/pull/36>`_)

------------------
* Added ``ParseString`` method to UInt160/UInt256 (`PR 35 <https://github.com/CityOfZion/neo-python-core/pull/35>`_)

------------------
* Added ``Fixed8.ToJsonString()`` (`PR 33 <https://github.com/CityOfZion/neo-python-core/pull/33>`_)

------------------
* Added UInt ``To0xString`` method

------------------
* Documentation update
* Moved the ``cryptography`` dependency to ``requirements_dev.txt``

------------------
* Added ``neo.Cryptography`` and ``KeyPair``
* Changed signature of ``neocore.Cryptography.Crypto.Sign()`` to remove unused ``public_key`` argument
* Removed redundant ``neocore.Cryptography.Helper.hash_to_wallet_address()`` function, use ``neocore.Cryptography.Helper.scripthash_to_address()`` instead.
* Removed unused ``neocore.Cryptography.Helper`` functions: ``random_string``, ``bytes_to_hex_string``, ``bin_sha256``, ``sha256``, ``random_key``.