+ clean up FASTQs in /tmp -- take two

  - this is a second refactor attempt after a discussion in [github
    genome pull request 301][1] and further offline discussion with @tabbott.

  - this is midway refactor.  @tabbott's original lambda suggestion is
    probably the best way to do things long-term, but the desired
    refactor may get unwieldy and out of scope for immediate needs.

    The basic goal is to place the temporary file deletion logic in the
    base class, rather than in the subclass.  This is because the input
    files supplied to the aligners get generated in the base class.

  - The Bwamem test:

       lib/perl/Genome/InstrumentData/AlignmentResult/Bwamem.t

    as been reset back to the original version before this feature
    branch started.

[1]: https://github.com/genome/genome/pull/301/