Chainside-btcpy

Fixes
* Minor fixes

Adds
* Additional unit tests for addresses
* Dump option to integration testing
* New hash functions on `Stream`

Fixes
* Public key derivation

Adds
* README paragraph on HD derivation
* test suite on HD derivation

Fixes
* Adapt recent API breaking changest to integration testing

Fixes
* A bug in new pubkey compression method
* A bug in script unhexlify

Backward compatibility
* `PublicKey`'s `compress()` method now returns a new key instead of changing the existing one

Added
* Support for SegWit addresses
* New module `hd`, providing support for BIP32 HD derivation

Fixed
* The `hd` module partially solves issue 1

Backward compatibility
Breaks the following old functionalities:
* `PrivateKey` and `PublicKey` `from_bip32()` methods no longer exist
* `AddressBuilder` no longer exists
* Though SegWit addresses were supposed to be created and used through the `Address` class, now a `SegWitAddress` class has been introduced for that purpose
* The `ScriptPubKey` `to_address()` method no longer expects an optional `bool` to specify segwit/non-segwit, it now expects a `segwit_version` that defaults to `None`