This PR will...

Update functional test runner to run locally with Safari, Chrome, and Firefox.

Example:
UA=safari npm run test:func

Also adds a demo page debug url for each failed test:

    5) should seek 3s from end and receive video ended event for HLS fMP4...
http://localhost:8000/hls.js/demo/?src=https%3A%2F%...

and a summary of asset urls failures:

Quitting browser...
Browser quit.
{
  "http://example.com/test1.m3u8": 7,
  "http://example.com/test2.m3u8": 1
}


  121 passing (10m)
  8 failing

Why is this Pull Request needed?

Legacy webdriver configuration is needed for saucelabs, but is unable to locate drivers locally on macos.

Are there any points in the code the reviewer needs to double check?

Resolves issues:

Checklist

• changes have been done against master branch, and PR does not conflict
• new unit / functional tests have been added (whenever applicable)
• API or design changes are documented in API.md