minor wifxes
Complete rework of the package:

  - filesystem watching (chokidar) and "client-side" templates replaced
    with direct JSON API over HTTP
  - replaced socket.io with EventSource (SSE)
  - dedicated Pane classes: ImagePane, PlotPane
  - replaced nvd3 with dygraphs
  - new .plot() API
  - renamed module litegfx -> display