P/R "extended m3u" support

[sosie-js]

Self service ;D

[xi]

Thanks for taking the time. I didn't have the time yet to dive into the details of extended m3u (I am not sure for example how a duration of 0 or -1 should be handled). But there are already some things you could do to help me review this:

• Please run flake8 on your code.
• flake8 no longer supports tabs, so I replaced tabs by spaces in the main branch. Please rebase your branch.
• I noticed you also made some other changes like adding examples and an -O parameter. Please open separate pull requests for those so we can concentrate on one thing at a time.