Add simulate function skeleton
Add general structure of simulate (untested)
Change comment headers more explicit
Fix unit-time-lapse to return a graph

It previously returned a vector in contrary to
what it claimed to do.
Change transmit to create :E nodes (not :I nodes)
Modify simulate to return a seq of graphs

This is more informative than just returning the state-freq
Add reproducible pseudo-random number to simulate
Change transmit-test to accomodate S->E transition

Before it was expecting S->I transition
Remove probablistic failure from target-ids-test
Add preliminary test for simulations
Merge branch 'feature-iteration-tracker' into develop