Add Submission and Comment Probability Environmental Variables to Heroku

[MrPowerScripts]

I would merge this if it was a bit more responsive and only pulled the values from the envars, otherwise use the default. but then it would keep parts of the config is separate places and i'm not sure how I feel about that right now. but I can look more into it this weekend and see if there's an elegant solution for all of this.

[ghost]

I’ll try to add that

[ghost]

I think this commit should do what you said.