Fix 'wrong arguments for function "buffer_set"'
Fix 'wrong arguments for function "buffer_set"'

When a "channel_joined" event is received (e.g. when joining channels
from the web client, or when someone else makes you join the channel),
update_from_message_json sets self.topic to the dict, but render_topic
expects it to be a string. This is an inconsistency introduced by
e64293b41573b5caad2ebf343d9a4397cef22a67. Let's keep the dict.

Actually, using update_from_message_json at all seems like a bad idea...

rawdigits/wee-slack,wee-slack/wee-slack,trygveaa/wee-slack