default_reply was read directly from slackbot_settings. This prevented
setting it with environment variables, using other settings files, and
other ways of changing settings outside of the slackbot_settings import.
This change makes it work like every other setting, and also renames
default_reply to DEFAULT_REPLY to make it match other settings. Because
some users might have a slackbot_settings file with default_reply set,
this change also converts default_reply to DEFAULT_REPLY.
default_reply was read directly from slackbot_settings. This prevented setting it with environment variables, using other settings files, and other ways of changing settings outside of the slackbot_settings import. This change makes it work like every other setting, and also renames default_reply to DEFAULT_REPLY to make it match other settings. Because some users might have a slackbot_settings file with default_reply set, this change also converts default_reply to DEFAULT_REPLY.