Renamed property renderOnAddition to renderOnAddRemove
fabric.Canvas.renderAll can now be disabled on removing objects (renderOnAddRemove = false)
Add tests for renderOnAddRemove (add, insertAt and remove)
jsdoc additions
Merge pull request #783 from Kienz/renderOnAddRemove

[BACK_INCOMPAT] `fabric.Canvas.renderOnAddition` is now `fabric.Canvas.renderOnAddRemove`. Closes #491