fix:issue #1420 增加skipEmptyDir参数

[delei]

fix: issue #1420 增加skipEmptyDir 参数。 默认为 true。当读取空目录时，跳过不抛出异常。如果需抛出异常则设置为 false

[kyle-magic]

met the same problem, skipEmptyDir is useful when u read HDFS by daily partitions, because sometimes there is no data in some partitions, it's not elegant to solve it in other script.