Single quote process arguments

Compatible with shell syntax (makes commands copy-paste able), and
allows users to definitively know what ran or is running.

This addresses #744
This has the unfortunate side effect that normal arguments which do not require a single quote end up getting single-quoted (which is why we're not just delegating to the `Show` impl of `std::io::Command`). Could this have some extra logic to not quote single arguments?

Could you also add a test for quoting arguments?