Consistent time loop

[odunbar]

Hi all, For the time loops for running epidemics/master equations, at some point i used a simple

for i in range(number_of_steps):

type loops for the time. This seems to be in all examples now, but it's likely a time based loop along the lines of say:
for time in forward_time_span:
for time in backward_time_span:
might be more appropriate.

It would be nice if we could find the best way to write it, and pass it into all examples.