sweepWrapper.m: update for crypt extinction

sweepWrapper.m was updated to include a -1 value if the stem cell
population falls below 0.1. It works for all input values, but still has
certain parameters for which it doesn't find the correct steady state.
This is found to be best at taking the last 5 data points and comparing
to the 5 before.
Merge branch 'master' of https://github.com/jleem10/GroupD_Project_Phase1