Reworded things in terms of frequency (instead of normalized_tally)
moved classif_rect.py to classif_table.py, and revised by_specimen terminology to be more intuitive
Overhaul of classif_table: Output behaviour much easier to understand, and more consistent. Everything forks on whether or not specimen map is specified.
Added assertion to the effect that specimen names should not be tax_id, tax_name or rank (this could break things, and would be silly anyway).
Added a deprecated version of the old classif_rect script
Merge pull request #312 from matsen/312-classif-rect-average-frequency

Clarify descriptions of `--normalize-by-specimen` flag functionality in scripts/classif_rect.py