Chainside-btcpy

Fixed
* Parsing of invalid pushdata ops

Added
* base58 native implementation

Fixed
* Parsing of peculiar multisig scripts

Backward compatibility
* Does not break past functionalities

Added
* Parsing of data structures is now way more efficient
* Opcodes have been isolated in a separate file and helper methods have been created to deal with them

Fixed
* Parsing of peculiar scripts no longer crashes (e.g. empy push operations, multisig scripts without public keys)

Backward compatibility
Breaks the following functionality:
* Any code that used the following static fields of the `BaseScript` class now needs to be refactored to use the `opcodes` module:
* `opcode_to_int`
* `int_to_opcode`
* `opcode_to_hex`
* `hex_to_opcode`

Added
* `CouldNotEncode` exception in codecs
* `force=False` option in network setup
* `check_network=True` in address validity check
* Notion of compressed public key in `PrivateKey` class
* `to_wif()` method in `PrivateKey`
* `.json` extension to test vectors
* Tests for all new features and fixes

Fixed
* Serialization of `OP_1NEGATE`
* Address in script `to_json()`
* Conversion to address in `P2wshV0Script`

Backwards compatibility
Some conversions from private key to public key might change as now `PrivateKey` remembers if it was created from a WIF format that demanded the generation of a compressed public key.

Added
* Better python3 compatibility
* `is_valid()` method in `BaseAddress` to check address validity
* Factory for SegWit scripts, to better handle versioning
* Hash pinning in dependencies

Fixed
* Make some methods private in `ExtendedPublicKey`

Backward compatibility
Breaks the following old functionalities:
* The `serialize_key()` method in `ExtendedPublicKey` has been made private (i.e. renamed to `_serialize_key()`)
* The `serialized_public()` method in `ExtendedPublicKey` has been made private (i.e. renamed to `_serialized_public()`)

Moves unit testing data in separate JSON files