Render empty row if all existing rows are removed

The empty row renders fine if initializing a table with an empty collection,
but if models/rows are removed the empty row is never rendered. This will call
`this.render` if the empty row is unshifted into `this.rows`.
Merge pull request #478 from marcneuwirth/empty-row

Render empty row if all existing rows are removed
Prevent moveToNextCell throwing exception when model is shared (fixes
#507)
Merge pull request #521 from christinedraper/fix507

Prevent moveToNextCell throwing exception when model is shared (#507)
Clean up
Update dist
Merge master from wyuenho#master