Starting to write VM

- Hand-wrote an assembly-language-ish file, so I can think through both
what I want the VM to do and what I thus need the compiler to generate.
 If it seems verbose, that’s because I like documentation; I’m
imagining I could generate human-readable assembly-language files, with
extensive comments, as well as very compact, numeric-only files with no
comments.

- Started writing parser for the assembly-language file.