Add subtitles, video, and audio group-id refs to StreamInfo

[cdunklau]

This partially addresses #121

I'm not sure about this... it seems like this could be a potentially breaking change, and I'm suspicious about the tests all passing with it. It seems to me that this (and #125) should have broken playlist serialization.

Please review.

[coveralls]

Coverage remained the same at 97.095% when pulling fb6ef2a on cdunklau:expand-streaminfo into 12550e3 on globocom:master.

[leandromoreira]

Hey @cdunklau thanks for the contribution, it is amazing such effort! In regard to your worries, I think this PR doesn't offer any breaking change, it adds features, therefore, all the tests should be passing without any issues.

[leandromoreira]

I would use fake uri (i.e: http://example.com/cc.srt) instead of `"cc".

CLOSED-CAPTION does not specify a Rendition; the closed caption
      media is present in the Media Segments of every video Rendition.

      URI

      The value is a quoted-string containing a URI that identifies the
      Media Playlist file.  This attribute is OPTIONAL; see
      Section 4.3.4.2.1.  If the TYPE is CLOSED-CAPTIONS, the URI
      attribute MUST NOT be present.

[cdunklau]

I think you're conflating the URI attribute of EXT-X-I-FRAME-STREAM-INF with the URI line that must follow EXT-X-STREAM-INF. In EXT-X-STREAM-INF, the CLOSED-CAPTIONS, AUDIO, VIDEO, and SUBTITLES attributes all reference a "GROUP-ID attribute of an EXT-X-MEDIA tag elsewhere".

However, reviewing this made me realize that StreamInfo for EXT-X-I-FRAME-STREAM-INF should have audio, subtitles, and closed-captions set to None explicitly.

All attributes defined for the EXT-X-STREAM-INF tag (Section 4.3.4.2)
are also defined for the EXT-X-I-FRAME-STREAM-INF tag, except for the
FRAME-RATE, AUDIO, SUBTITLES, and CLOSED-CAPTIONS attributes.

[leandromoreira]

Do you plan to do any other PR soon? I'm thinking to release a new version.

[cdunklau]

@leandromoreira No concrete plans, no. I'll probably take another look at #121 next week, but it seems like the other issue there will take some more digging.