Fixed BarRenderer tests.
Fixed BarRenderer tests.

They were expecting the domain to include zero, which was not the case
after c2df854.

There should be a better story on how to specify that the domain of a
QuantitiveScale should always include 0; This issue has been filed as #219.

Close #217.

iobeam/plottable,gdseller/plottable,danmane/plottable,iobeam/plottable,jacqt/plottable,NextTuesday/plottable,RobertoMalatesta/plottable,palantir/plottable,danmane/plottable,onaio/plottable,danmane/plottable,gdseller/plottable,jacqt/plottable,RobertoMalatesta/plottable,softwords/plottable,palantir/plottable,alyssaq/plottable,onaio/plottable,NextTuesday/plottable,softwords/plottable,jacqt/plottable,iobeam/plottable,RobertoMalatesta/plottable,palantir/plottable,alyssaq/plottable,palantir/plottable,NextTuesday/plottable,softwords/plottable,gdseller/plottable,onaio/plottable,alyssaq/plottable