Usage
For ELM, "recursive" refers to Eq(10), "comb" refers to Eq(9), and "comb_orig" refers to Eq(8) in the Errata (http://tommyjcarpenter.com/papers/2014/car_pools_errata.pdf) and paper here (http://tommyjcarpenter.com/papers/2014/pools_ITS.pdf)
>>> from queueing_models import engset_loss_model as elm
>>> elm.elm_recursive(.5, 1000, 5)
0.9899701531080783
>>> elm.elm_comb(.5, 1000, 5)
0.9899701531080783
>>> elm.elm_comb_orig(.5, 1000, 5)
0.9899701531080783