Rbar is now a function

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
added normalize_vector function

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Successive substitution moved into a class for easier data handling

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
More derivatives, now understand how to implement Newton-Raphson!

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>