Example of using modules within the same file, long pathing to modules introduced, how to make functions not private not yet shown.
Some stuff about the use statement, 'pub' introduced, how to import multiple function symbols
not introduced.
Some confusing things about using super:: and self:: in module imports -- not for OO to disambiguate what functions are referenced.  Hopefully won't need this part soon :)
Defining stuff in modules. Use 'mod' and 'pub mod'.  Pub mod only seems neccessary for lower level
bits.  Still accessed with use?
How libraries work -- "extern crate"
Remember that this static linking, we can delete the .rlib and the executable is fine.