Keep same reference on data and values for scatter
Remove setup of `singlePoint` variable that is not used in some of the bar models.

Additionally, this variable was being assigned as a property on the global object (`window` in browsers) instead of being declared locally with a `var` statement.
Merge pull request #257 from JustinTArthur/remove-unused-global-singlePoint-var-assignments

Remove singlePoint variable that is assigned but not used in bar models.
Merge remote-tracking branch 'origin/master' into development
Merge branch 'fix-dereferencing' of https://github.com/Marsup/nvd3 into master-issue240
Merge branch 'master' into development