Simplify setup (configuration and token generation)

[patcon]

Reticketed from #10 (comment) (I had related questions)

Curious your thoughts on this!

Do you think that goal (simpler config) might involve web api anyhow? the thinking being that config could then just be "register a new app", and then it's simple in-browser oauth for two teams stored in some backend.

or we're you more thinking along the lines of a CLI wizard and envvars?

[wdoekes]

Well, for starters, begin removal of the horrendous CONFIG dict and replace with ini-file loading like this:

[DEFAULT]
WEBHOOK_IN_URL = https://hooks.slack.com/services
WEBHOOK_IN_URL_OSSO = ${WEBHOOK_IN_URL}/X/Y/Z
WEBAPI_TOKEN_OSSO = xoxp-token-token-token

[company1-osso]
A.webhook_in_url =
    ${WEBHOOK_IN_URL}/AAAAAAAAA/BBBBBBBBB/cccccccccccccccccccccccc
A.webhook_out_token = dddddddddddddddddddddddd
A.channel = CXXXXXXXX
A.peername = osso
A.webapi_token =
 
B.webhook_in_url = ${WEBHOOK_IN_URL_OSSO}
B.webhook_out_token = eeeeeeeeeeeeeeeeeeeeeeee
B.channel = #shared-company1
B.peername = company1
B.webapi_token = ${WEBAPI_TOKEN_OSSO}

Splitting it up into several files will add the need for a setup.py, but also make refactoring/testing easier.