Tip Request: `commands.Greedy`

[Skelmis]

This does not need to be a tutorial, and I feel it could piggy back off your /tips/optionals file. I do however feel that it is a good idea to include this as it would certainly help people out and would fit nicely into an 'Arguments' tip page.

[vcokltfre]

I plan on redoing the optional page anyway, so I'll put a bunch of information about arguments in general in there, including this