Demo issues: Broken video link, missing control icons

Issues

The demo pages at demo/index.html and build/index.html have a few issues.

1. Video link is broken for "Video Player" example due to protocol relative URI.

Suggest changing file path from //github.com/mediaelement/mediaelement-files/blob/master/big_buck_bunny.mp4?raw=true to https://github.com/mediaelement/mediaelement-files/blob/master/big_buck_bunny.mp4?raw=true

2. Toolbar icons are missing

For both video and audio examples, the icons on the toolbar are missing. The buttons and functionality are still present, though.

Environment

mediaelement-7.0.7