M3u8

* support hls attributes video, audio, subtitles and cc
* support hls tag `EXT-X-DISCONTINUITY-SEQUENCE`

* add support to tag `EXT-X-START`

* some bug fixes
* adds support to commas on title
* adds support `CLOSED-CAPTIONS`

* adds [`EXT-X-MAP` tag](https://tools.ietf.org/html/draft-pantos-http-live-streaming-21#section-4.3.2.5)

- enables user to send request http header

- **WARN** Changed API: instead of using `m3u8_obj.key` use `m3u8_obj.keys`
- adds multiple keys
- supports SCTE35 cue markers for envivio and elemental

Thanks birme bertothunder acurro