OstapHEP/ostap: v1.6.4.2

v1.6.4.2 New features: add more decorators for TCollection and TSeqCollection: get, 'getitem' , 'contains' few tweaks for ostap.plotting.canvas module add += operator for ROOT.TCollection allow to specify colors by names for xxx.draw ( ... , _color= ) commands add analytic non-symmetric expression for 3-body phase space via elliptic integrals small fix for reweighter (thanks to Daria Savrina) Backward incompatible Bug fixes: fix failing test