[Initial import.
Will M. Farr **20070815143202]
[TAG 1.0
Will M. Farr **20070815143217]
[Added deriv? predicate.
Will M. Farr **20070815162405]
[Updated documentation to refer to version 2.
Will M. Farr **20070815162529]
[Added contracts to exports.
Will M. Farr **20070815180633]
[Fixed bug where inner derivatives could remove deriv structures associated with outer derivatives and extract-derivative would return an error instead of 0. (Reported by Barak A. Pearlmutter.)
Will M. Farr **20070823130442]
[Fixed bug where tags were being constructed in increasing order, but heap property expected decreasing tags.
Will M. Farr **20070823220816]
[Added gradient, jacobian to deriv-lang.ss.
Will M. Farr **20070904214029]
[Added scribble documentation.
Will M. Farr **20070904214109]
[Extra doc for jacobian.
Will M. Farr **20070904221242]
[Better documentation for gradient and jacobian.
Will M. Farr **20070904221816]