饼图外显示百分比，labelLine控制与环的距离

示例：

function lossTenants(){
    var myDailyEn = echarts.init(document.getElementById('lossTenants'));
    option = {
        tooltip: {
            backgroundColor: '#fff',
            textStyle:{
                color:'#545EFF'
            },
            formatter: "{b}:<br> {c} ({d}%)"
        },
        legend: {
            show:false
        },
        color: ['#15D3FF','#FFE418','#FB497C','#47DDE8','#656EFB'],
        series: [
            {
                name:'',
                type:'pie',
                radius: ['54%', '70%'],
                label: {
                    formatter: '{d}%'
                },
                labelLine:{
                    show:false,
                    length:8,
                    length2:8
                },
                data:[
                    {value:25, name:'物业服务差'},
                    {value:5, name:'环境差'},
                    {value:30, name:'生意不好'},
                    {value:20, name:'租金高'},
                    {value:20, name:'其他'}
                ]
            }
        ]
    };
    myDailyEn.setOption(option);
}