add Secant.py to project2
update secant, add root_finder_examples
update root_finder_examples
finish Secant.py and root_finder_examples.py
add growth_logistic2.py
add text2func
add fit_pendulum_data
add pendulum.dat
add Integral_eff
move Integral_eff to correct location
add simulate_binomial
add strategies4guess.py
add body_in_fluid.py
add body_in_fluid_termvel.py and ODESolver.py