Allow user to specify R0 (in lieu of doubling time)

[sam-writer]

Calculation (extends "more info about this tool"):

We can compute the implicit $R_0$ from our doubling time inputs and our assumed duration of infectiousness $(1/\gamma)$. Since $R_0$ is the number of additional individuals infected by each infected individual when $I << S$, we can compute the growth rate $g$ as a function of $R_0$ and $\gamma$:
$$g = \gamma R_0 $$
From our previous equation for $g$, we can substitute and rearrange to find:
$$R_0 = (2^{1/T_d} - 1)/\gamma$$

So, for our $\gamma$ of 1/14 days, a doubling time of 4 days corresponds to an $R_0$ of 2.65.

[sam-writer]

@cjbayesian is this already implemented?

[cjbayesian]

We opted to display the R0 being implied at the doubling rate specified. We also now display the effective R0 conditional on social distancing.

I think we can close this.

[mdbecker]

@sam-qordoba I think this is a won't-fix. Can you see a reason to do otherwise?

[sam-writer]

This seems like a wont-fix to me as well. Though, as we try to make the code more modular, one goal can be if the user imports the code to use in python, they should be able to specify R_0