v0.1.2

• Fix TypeError: Can't instantiate abstract Handshake class without defining '_REQUIRED_CLASS_VARS' classvar occurring when trying to initialize any Packet class, due to a typo.
• Fix TypeError: Can't instantiate abstract Handshake class without defining '__slots__' classvar explicitly(__slots__ found in a subclass, but not explicitly in Handshake) occuring when using the Handshake packet, due to (requiried) __slots__ class variable not being defined.