Harden the `module` macro

[Olical]

Steps to reproduce bad things:

• Had a Lua file on disk with bad code in it that won't compile etc under the module path foo.bar.
• Start or edit a Fennel file with (module foo.bar) inside.
• Get errors as Aniseed's module macro tries to require the bad module.

You can fix this by deleting the bad Lua and restarting or (tset package.loaded :foo.bar nil) I think? Possibly other things to work around this too. I want to make it so a bad pre-existing module that won't require / throws errors will be caught and ignored. If the existing module is borked, let's just pretend it doesn't exist.

[Olical]

Initial report of this issue:

[Olical]

Think this is doneeee