Set tooltip to show extent of sparkData (#3626)
Set tooltip to show extent of sparkData (#3626)

* Set tooltip to show extent of sparkData

* Using d3format instead of round

timifasubaa/incubator-superset,airbnb/superset,zhouyao1994/incubator-superset,timifasubaa/incubator-superset,mistercrunch/panoramix,dmigo/incubator-superset,zhouyao1994/incubator-superset,airbnb/caravel,zhouyao1994/incubator-superset,airbnb/caravel,mistercrunch/panoramix,apache/incubator-superset,airbnb/superset,alanmcruickshank/superset-dev,zhouyao1994/incubator-superset,airbnb/caravel,timifasubaa/incubator-superset,mistercrunch/panoramix,mistercrunch/panoramix,airbnb/caravel,zhouyao1994/incubator-superset,apache/incubator-superset,apache/incubator-superset,airbnb/superset,airbnb/superset,alanmcruickshank/superset-dev,timifasubaa/incubator-superset,dmigo/incubator-superset,alanmcruickshank/superset-dev,alanmcruickshank/superset-dev,apache/incubator-superset,dmigo/incubator-superset,apache/incubator-superset,dmigo/incubator-superset