[commands] Change UserConverter to actually work with User, not Member.
[commands] Change UserConverter to actually work with User, not Member.

variablehair/Eggplantato,Harmon758/discord.py,khazhyk/discord.py,mgardne8/discord.py,Rapptz/discord.py,Harmon758/discord.py,rapptz/discord.py,imayhaveborkedit/discord.py