bots: Make giphy bot consistent with other api_key bot structure.
ADD
zulip_bots/zulip_bots/bots/giphy/giphy.conf
+[giphy]
+key = 12345678

MODIFY
zulip_bots/zulip_bots/bots/giphy/giphy.py
zulip_bots/zulip_bots/bots/giphy/giphy.py
# To use this plugin, you need to set up the Giphy API key for this bot in
-# ~/.giphy_config
+# giphy.conf in this (zulip_bots/bots/giphy/giphy/) directory.
from __future__ import absolute_import
from __future__ import print_function

bots: Make giphy bot consistent with other api_key bot structure.