[web-audio-api] Make AudioContext and AudioNode Lifetime sections informative (#196)

> Originally reported on W3C Bugzilla [ISSUE-21523](https://www.w3.org/Bugs/Public/show_bug.cgi?id=21523) Tue, 02 Apr 2013 14:46:35 GMT
> Reported by Olivier Thereaux
> Assigned to 

Per discussion at Audio WG f2f 2013-03-26

The two sections:
https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/specification.html#lifetime-AudioNode
and 
https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/specification.html#lifetime-AudioContext
should be informative

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Reply to this email directly or view it on GitHub:
https://github.com/WebAudio/web-audio-api/issues/196