glob list instead of simple hdfs list and pattern support for input

Right now hraven accepts a simple hdfs path as input folder and will fetch all job history + conf files underneath it. This pull request adds support for specifying a pattern with wildcards (*) and using hdfs api's globStatus method to list files instead of hraven's recursive listFiles method. This way one can easily shard hraven's job to different years/months/days.
So each year you would have to manually adjust this to the new year ?
I'm pretty sure that we'd forget to make this change on January first in a daze of New Year and we'd have collection broken.