Changed
- `PipelineInterface` now derives from `peppy.AttributeDict`.
- On `PipelineInterface`, iteration over pipelines now is with `iterpipes`.
- Rename `parse_arguments` to `build_parser`, which returns `argparse.ArgumentParser` object
- Integers in HTML reports are made more human-readable by including commas.
- Column headers in HTML reports are now stricly for sorting; there's a separate list for plottable columns.
- More informative error messages
- HTML samples list is fully populated.
- Existence of an object lacking an anchor image is no longer problematic for `summarize`.
- Basic package test in Python 3 now succeeds: `python3 setup.py test`.