adds midpoint interpolation to stepped plots#5908

Merged

simonbrunel merged 3 commits intochartjs:masterfrom veggiesaurus:midpoint_step_interpolation

Dec 18, 2018

+149-2

Commits on Dec 12, 2018

Commits on Dec 18, 2018

adds unit tests and switched from 'midpoint' to 'middle'
veggiesaurus
committed