set sample histograms in __init__
Merge pull request #550 from ndawe/master

[MRG] HistFactory: set sample histograms in __init__
histfactory: rm make_model and make_models. Use make_workspace
Merge pull request #551 from ndawe/master

[MRG] histfactory: rm make_model and make_models. Use make_workspace
update plotting example
fix find_all_primitives
Merge pull request #552 from ndawe/master

[MRG] fix regression in find_all_primitives
showstack -> show_stack
Merge pull request #554 from ndawe/master

[MRG] showstack -> show_stack
translate ! to not_ in Cut.safe()
Merge pull request #555 from ndawe/master

[MRG] translate ! to not_ in Cut.safe()
add TArrow
return the axes bounds from utils.draw
Merge pull request #556 from ndawe/master

[MRG] add TArrow
Merge pull request #557 from ndawe/master

[MRG] return the axes bounds from utils.draw
fixing graph division
Merge pull request #558 from kreczko/fix_graph_division

fixing graph division
use asrootpy in List.__iter__ and ObjArray.__iter__
Merge pull request #559 from ndawe/master

[MRG] use asrootpy in List.__iter__ and ObjArray.__iter__
use keepalive in Legend.AddEntry