用法示例：
// height and width in pixels
var width = 800 , height = 600 ;
// describe where to put the chart and how big it is
var barChart = BarChart ( document . getElementById ( "container" ) , width , height ) ,
data = [ 3 , 0 , 4 , 5 ] ;
// set title and axis labels
barChart . setTitle ( "Demo" ) ;
barChart . setLabels ( "x" , "y" ) ;
// put the data into the bar chart
barChart . update ( da
