Changes to taxonomy class

Updated to have the taxonomy names as class constants for reuse in
templates.
Merge pull request #2 from randybuildsthings/taxonomy-fix

Changes to taxonomy class
More taxonomy wrangling

Renamed the one-price taxonomy to be a "low price" taxonomy, and then
created an additional "high price" taxonomy. Updated the initialization
code to register both properly.
Merge pull request #3 from randybuildsthings/taxonomy-fix

More taxonomy wrangling
Merge pull request #5 from randybuildsthings/master

Changes to taxonomy class