instead of manually adding event listeners, let react handle event
listener lifecycle. This means HLS will not throw in enzyme
environment and we don't have to clean up any handlers manually
* prepend newly plotted signal to show first
* highlight selected available message in navigation
* extract CanGraph render function in explorer
* toggle expanded signals in Legend, trigger edit and plot when expanding signal
* check if plottedSignal is new before plotting
* add uid to signal model
* use signal uid in SignalLegend and entry for keys and expanding
* adding sass npm script to watch scss files
* refactoring most of markup for semantic class naming, introducing scss files, light styling
* prefer flex over floats
* set min-width on body
Chris Vickery