Support timestamp filtering and byte object as input/output

[ChunYaoChang]

This request contains two commits:

1. Support timestamp filtering in mi2log file. Users now can pass in start_timesetamp and end_timestamp to OfflineReplayer so that it only contains logs within the start-end interval.
2. Support byte object as input/output. For input part, I add a function set_input_file(object) in OfflineReplayer for users to pass in byte object directly. For output part, users can access the byte object via OfflineReplayer.output_bytes_object.