created dummy functions for different SIR models, made the default SIR
model as simple as possible. Different models can now be loaded with
example, e.g. example(SIR), example(SIR_stoch),
example(SIR_reporting). This is nice because it preserves comments in
the code, and allows to revert to the original after one has made
changes. I'd suggest a similar strategy for SEITL, if this can be made
to work.
updated doc
test data set
Merge remote-tracking branch 'origin/master'