This MR is quite a big refactoring of the
cara.models definition (so ping @mrognlie). In it, I:
- Fix #14 (closed) by re-writing the concentration equation, and recognising that we had an
ifstatement in there for no other reason than the equation was formulated slightly differently in the first place. In reality, a bit of algebra shows that the two branches were effectively the same thing.
- Pull out the concept of intervals from ventilation and the infected person definition, thereby giving us some flexibility in how we want to define time ranges
- Note that this means that the way to build a model has changed - it is likely to break !8 (merged).
- Update the existing app to use the new scheme
- Add some tests to validate that the new scheme is doing what we want