[acast] Fix broken audio URL and timestamp extraction

[wader]

Before first bling was used now we look for the first bling with
type BlingAudio

Before publishingDate was a ms unix timestamp now it is iso8601.

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Fix broken audio URL and timestamp extraction for acast.

[wader]

@remitamine

[wader]

Not sure about this. README says timestamp should be "UNIX timestamp of the moment the video became available" but not if it should be seconds of milliseconds etc

[wader]

Not sure about this. This is because of https://github.com/rg3/youtube-dl/blob/master/youtube_dl/YoutubeDL.py#L1287

[remitamine]

for the timestamp, i added it wrong in the wrong way. it should be in seconds(now with your change it's correct).

Before first bling was used now we look for the first bling with type BlingAudio.

if you have a url that have multiple blings than add a test.

[wader]

@remitamine thanks for review! i've added a test with multiple blings nows

[remitamine]

Would you like to be listed in AUTHORS? If so under what name?

[wader]

Thanks. Sure, Mattias Wadman

[remitamine]

Done.