A few renderers default updates#1571

Merged

jonmmease merged 3 commits intomasterfrom

renderers_updates

May 25, 2019

Commits on May 21, 2019

Init notebook* renderers at the end when set with `init_notebook_mode`
jonmmease
committed
Set _to_activate list rather than extend so that it doens't keep growing
jonmmease
committed
Use notebook rather than notebook_connected in default v4 renderer
jonmmease
committed