New files and tuning

Added contributing information, stripping out some unnecessary features
that will be reinserted once an actual use case appears.
Remove Haven login

Safe Haven model no longer requires login. Feature was there as an
example, but is not needed.
Remove SlowSIR

Removing SlowSIR model.
Merge pull request #1 from epimodels/SciPy-Cleanup

SciPy Cleanup