Convert distribution system to conda-forge

[bstabler]

Just like activitysim, see ActivitySim/activitysim#424

[bettinardi]

Hopefully a low lift to migrate PopSim in a similar way that ActivitySim was migrated. I'm not sure how much this adds, but I would like PopSim to be installed with the ActivitySim installer - one install for everything being developed under ActivitySim...

[brynpickering]

The main blocker will be or-tools, which has issues of its own with building a conda-forge recipe on windows and macos: conda-forge/or-tools-feedstock#9.

If or-tools could be an optional dependency and cvxpy the default solver then there wouldn't be the same issues.