Range selector for loop-grid.
var Selector = require('loop-grid-selector')Returns an extended instance of ObservGrid with shape specified.
Pass in an observable ArrayGrid. done will be called on stop or before subsequent start.
Any truthy values will trigger a selection. Simultaneous true values will trigger range selection. selection will have .set(selectedIndexes) called on every change.
Sets selection to an empty array.
Release watch of inputGrid and call done.