Utilize NIO ByteBuffer in serialization

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NIO provides a useful type for serializing stuff into byte stream, ByteBuffer. Actual implementation simply concatenates output into [UInt8]. ByteBuffer covers this function way better.

Affected types

• OSCConvertible protocol that defines serialization, particularly
  • var oscValue: [Byte]? { get } - provides serialized value as bytes array
  • init?(data: [Byte]) and init?(data: ArraySlice<Byte>) constructors. They make up types from bytes stream
• conversion module is where serialization stuff takes place
  • extract.swift the entry point of decoding OSC packets.
  • Constructors of OSCMessage and OSCBundle where all the decoding happens.
• Tests/OSCCoreTests/ValueConversionTests test suite.

This ticket also affects #16

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Also consider testing serialization via NIO's preferred testing tool ByteToMessageDecoderVerifier