The last commit (fc6c30ec32) was affected
by a floating point addition/subtraction precision bug. The bug caused
nonsensical categories to appear on the audio feature bar charts. Now
fixed.
Fixes#51. Instead of passing in an array of hard coded values as the
interval end points, an object specifying the beginning, the end, and
the step size is used. Categories can be more easily defined and
modified this way.
