Provide a API to specify MIN_REMEMBER_DURATION for files to consider as input in streaming

Currently, only one API called textFileStream in StreamingContext to specify the text file dstream, which ignores the old files always. On some times, the old files is still useful.
Need a API to let user choose whether the old files need to be ingored or not .

The API currently in StreamingContext:
def textFileStream(directory: String): DStream[String] =

{ fileStream[LongWritable, Text, TextInputFormat](directory).map(_._2.toString) }