Improve default tooltip when data is a string. Fix #3307
Improve default tooltip when data is a string. Fix #3307

starlkj/echarts,apache/incubator-echarts,chenfwind/echarts,apache/incubator-echarts,ecomfe/echarts,100star/echarts,starlkj/echarts,ecomfe/echarts,starlkj/echarts,100star/echarts,chenfwind/echarts