Add and use generic playlist attribute list parser

[kanongil]

This fixes order dependent parsing of EXT-X-STREAM-INF attributes.

This also exposes any stream info attribute for external processing.

Tested to work on a normal and encrypted stream in Chrome.

[mangui]

I would be keen to merge this, but it would be good to add some unit tests to cover the new parsing code, so that in case it breaks anything or if we modify it later on, we can easily spot any regression.
you can add your test playlist for example, I will complement it with mine ...

[mangui]

related with https://github.com/dailymotion/hls.js/pull/106

[kanongil]

Updated with tests, which are failing due to old node version on travis.

[kanongil]

Anything you are missing here?

[mangui]

@kanongil
thanks for the attr-list unit tests.
I need to check that the whole parsing still works with a bunch of playlists, so it will require a little bit more time before I can merge.
best would be to add some unit test on the playlist parsing as well. I know we don't have any at the moment ..

[mangui]

Hi @kanongil i am not clear about this new dependency to babel ?

[kanongil]

mocha does not understand es6 code and needs a compiler, which I register using --compilers js:babel/register. As such it needs to be declared a dev dependency as well.

[mangui]

fine, I will give it a hand soon

[mangui]

merged, I also added a couple of unit tests to cover manifest parsing code ...