Extract OpenHatch-specific details in a configuration file

[jdm]

There are lots of Python constants that could be moved into a configuration file instead of being hardcoded. This would make configuring a non-OpenHatch bot easier, and allow staying up to date with changes to WelcomeBot without having to merge.

[shaunagm]

This is an excellent point. We already have to do a bit of set-up to avoid this issue with the generated nickname file, so we can easily accommodate setting up a separate config file. Labelling and accepting this. Do you want to work on this yourself?

[jdm]

I'm considering it, since I'd like to run a bot for Servo's IRC channel. I'll leave a note here if I start working on it.

[aaparella]

Began work on this (PR #49). Open for critique :)

[pdurbin]

As I mentioned in IRC to @shaunagm I'm expecially interested in being able to configure the welcome message in a config file.

@aaparella I don't see that at https://github.com/aaparella/WelcomeBot/blob/configparser/settings.ini from a quick look. Would you be able to add the ability to put the welcome message in the config file?