Add HackCommand struct with methods for operating on tokenized commands. Finish readAndTokenize() by making it just return the command slices.
Add beginnings of mnemonic translation to binary for Go-based assmblr
Further development on assmblr command translation. The 'only' thing left is to correctly handle variable symbols. This will likely necessitate a redesign of how that's done.
Rework the main logic for processing A-cmd symbols.

First do a pass-through to add all labels to the symbol table. Then on the second pass process as usual. This way we can directly generate addresses for unknown variables.