Document that Client.get_channel works with PrivateChannel too.
Document that Client.get_channel works with PrivateChannel too.

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