JSON display fails when date range doesn't render plotly graph

[quadrophobiac]

Currently the default view of an endpoint will not display a graph or any JSON if it's outside of the last 30 days, per what's noted in the readme, HTML
which will redirect to a default time-range of the last 30 days)

Either decoupling the JSON and Plotly rendering or a simple UI message to the effect that this is the last 30 days might be helpful here given that this is the same end state for a user who supplies an incorrect date or no data value at all - see #105

[quadrophobiac]

I think this has been fixed by PR 200
plotly container now displays No data detected for selected range, please customise date range via the Dates tab below when it cannot render a graph