Tests and performance improvements

All of the remote commands are now covered by tests. This surfaced a few issues like getting volume at 100% would return 10, all of which have been fixed. The response from commands is now parsed for errors. The way packets were created and sent has also been optimized to be faster and allocate less which in turn brings about a 2x performance improvement for all of the commands.

Useful cli and fully working API

The interactive mode for the command line interface is now working well and all APIs are now working as expected.
Tests have been added and some API naming has been improved.

Interactive command terminal and API

This is an initial release containing a simple interactive cli terminal for sending commands easily. It also has a Go package implementing all of the IP control APIs supported by the amplifiers (at least those known from the documentation).

Known issues: Input source mapping is not working correctly yet.