Make default behaviour target rust when no argument is passed

[RodrigoAroeira]

While cargo-wipe is a useful tool to remove these unwanted directories, it makes no sense to associate the other languages to the cargo tool.

To maintain backwards compatibility, I propose that, when no language is passed, it defaults to rust, while keeping the option to optionally pass a language.

Additionally, another binary could be packed alongside cargo-wipe called only wipe that requires a language parameter to be passed