ODE wrapper for SciPy odeint

[Jay Wang]

As was asked, if you want to use odeint from SciPy with any of the programs in the book, then get the ODE wrapper here,
http://www.faculty.umassd.edu/j.wang/book/prog/ch02/Program_2.10_odewrap.py,
rename it to odewrap.py.

Then replace import ode with
import odewrap as ode

All the programs using RK2, RK4..., solvers (but not leapfrog) should work seamlessly.
This way you also get the benefit of adaptive step size of odeint.