"shell" now runs each program in a new lua environment, instead of
sharing that lua environment between all programs launched under a one
shell. Said environment now includes an implemenation of "require" and
the "package" API, so that programs can require modules into that
environment.
This means that programs can require in libraries without polluting the
global namespace, and without breaking the virtual computer model, as
each program has it's own set of requires, which are discarded when the
program ends.