["dash"] catchup to pull 273 (v1.1)

[quinn-dougherty]

Description:

pull 273 offered a radical new functionality https://github.com/CodeForPhilly/chime/pull/273

in production as of v1.1 https://pennchime.herokuapp.com/ there is a button you can press I know the date of the first hospitalization, and if you press that button the code will infer doubling time. If you do not press the button, the code will infer the date of first hospitalization.

Someone please port this functionality to dash.

[x] This is something we can copy over from streamlit (screenshots if applicable)

if possible, something as nice as st.date_input for date input

important note: as of this writing, dash3 is the branch that's properly rebased, the dash branch is not properly rebased.

[quinn-dougherty]

closed in pull 394, continued in https://github.com/CodeForPhilly/chime/issues/398