Skeleton of matching code and implementation of _calc_lunch_groups_sizes.
s/users/lunchers/g
Add LunchGroup class and TooManyLunchersInGroupException.
Fix a bug with _calc_lunch_group_sizes.
Add distance functions.
Finish grouping algorithm.
Use random numbers for distance for now.
Shortcircuit out of calc_lunch_group_sizes.
Merge branch 'matcher'