updating data when only updating graph data

[mg1075]

In the case of updating data on a short interval - e.g., one second - the update approach in this directive may not be optimal.

https://community.plot.ly/t/what-is-the-most-performant-way-to-update-a-graph-with-new-data/639

Looks like it should be using either extendTraces or restyle methods from plotly.