Updated BFGS minimization routine to use gradient-fn to estimate f-prime
when it is not provided. This also entailed changing gradient-fn to
accept matrices as well as vectors.
Fixed so tests pass. f-prime needs to be passed as a keyword argument.
Updated documentation to match new use of f-prime.
Merge pull request #218 from JackSullivan/merge-minimize-f-prime

Updated BFGS minimization routine to use gradient-fn to estimate f-prime
move core to protocol based dataset implementation
update excel for new dataset implementation
update io unit tests for new dataset implementation
update sql for new dataset implementation
update zoo for new dataset implementation