Miscellaneous changes in Args
Miscellaneous changes in Args

- Do not be lazy and DO add an example for the `_*` methods.
- Reorganize the methods so they're more coherent.
- Use the `rest` method than to rely on deref (which in turn relies on `full`).

acdenisSK/serenity,zeyla/serenity,Flat/serenity,Lakelezz/serenity,zeyla/serenity.rs