[x] Makes an empty plotly figure upon instantiation
[x] Has an add_data method, which takes a pandas data frame. The optional arguments are time_key='Time', inc_key='Incidence Number', and add bar plot trace of the incidence numbers to the figure with one bar per unit of time. Use the column keys as axis labels. Label the data as 'cases'.
[x] Has an add_simulation method, which takes a pandas data frame. The optional arguments are time_key='Time', inc_key='Incidence Number', and add bar plot trace of the incidence numbers to the figure with one bar per unit of time. Label the data as 'simulation'.
Create a figure class that uses plotly and: