use a bigger maximum value for the elevation widget

[karussell]

Currently we scale the y-axis of the elevation widget depending on the incoming data and so even small changes between e.g. 110m and 130m look huge despite being distributed over a few kilometers. Should we use e.g. "min elevation + 500m" as maximum value? Or e.g. use 0m as min elevation? And somehow consider the length of the route when picking the (min and) max elevation of the widget?

[easbar]

You can try changing this here: https://github.com/easbar/Leaflet.Heightgraph/blob/a1014641c35c43490b31cb25d3072e6c1237ed0e/src/heightgraph.js#L461-L476 (in the mapbox branch).