fix: add_histograms() output visualization errors (#82)

* fixed force option, fixed multiple args

* fixes to hadd logic, storing histograms in dict now...need users to be able to store two files worth of hists in memory

* Adjusting where should flow=True

* changed the way taxes were created, identify.to_axis seemed to change the edge values

* Now creating to_axis objects without including bin edges as arguments...