Wrote help for positive label option.
Implemented reporting options.

* Added --report <report> --to <file> options for specifying what
  reports to do and where the output should go.  The options can be used
  for requesting multiple reports to multiple outputs.
* Added class to handle reports.  Moved existing YAML report to new
  class.
* Changed main environment to handle lists of option arguments (needed
  for multiple reports).
* Added convenience methods (putList, getLast) for writing and reading
  the environment list values.  Switched all environment access to this
  new approach.
* Added convenience method for opening output.
* Added report for only ROC points.
* Wrote help for new options.
* Added test for new reporting options.
* Updated dependencies in makefile.
* Considered names of reports and how to design reporting for presenting
  information in various formats.