Support for QSEQ parsing.

This relates to issue #389.  @audy, @wasade.

Added parse_qseq, QseqIterator, support in the factory for .qseq and .qseq.gz.  Added unit tests.

For Sequence ID, I am using: "machine_name"_"run_number":"lane_number":"tile_number":"x":"y"#"index"/"read".  Example: CRESSIA_242:1:2204:1453:1918#0/1.  Do you agree?

I set qual_id to seq_id.  Do you agree?


We're planning to refactor the I/O in scikit-bio next week, so I think it's fine to leave the functions here for now and we'll take care of moving them during the refactor.