Fix Channel.permissions_for attribute error.
Fix Channel.permissions_for attribute error.

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