message: added demo files using CDNs
diff: - Shapes: How to add vertical lines [\#272](https://github.com/gitbrent/PptxGenJS/issues/272) ([simonjcarr](https://github.com/simonjcarr))
  **Implemented Enhancements:**
  +- Updated pptxgenjs-demo files to use CDNs instead of local files ([gitbrent](https://github.com/gitbrent))
  - Mis-detecting Existence of Node.js [\#277](https://github.com/gitbrent/PptxGenJS/issues/277) ([adrianirwin](https://github.com/adrianirwin)) ([DSheffield](https://github.com/DSheffield))
  -
  ## [v2.1.0](https://github.com/gitbrent/pptxgenjs/tree/v2.1.0) (2018-04-02)
  [Full Changelog](https://github.com/gitbrent/pptxgenjs/compare/v2.0.0...v2.1.0)
  