Allow usage of iterable object in Blob constructor.

[octet-stream]

I've noticed that Blob constructor can accept iterables as blobParts argument. This was tested in Chrome, Firefox and Safari. I also found tests for this case in WPT. See: https://github.com/web-platform-tests/wpt/blob/e7d848ca78a17253dde9d49956bc00ae3ba91c57/FileAPI/blob/Blob-constructor.any.js#L58-L105
This PR fixes how constructor threats iterable objects.

[codecov]

Codecov Report

Merging #108 (fabbd8a) into master (0b02843) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #108   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            4         4           
  Lines          411       412    +1     
  Branches        60        60           
=========================================
+ Hits           411       412    +1     

Impacted Files	Coverage Δ
index.js	100.00% <100.00%> (ø)

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[octet-stream]

@jimmywarting tests for blobs backed up by fs failing for some reason, but everything related to this patch seem to be working.

[jimmywarting]

👍

Think I got one idea of how to use WPT test

tests for blobs backed up by fs failing for some reason, but everything related to this patch seem to be working.

The test are a tiny bit racy... that is why it fails sometimes and sometimes it's not

[octet-stream]

The test are a tiny bit racy... that is why it fails sometimes and sometimes it's not

AVA runs tests concurrently (asynchronous tests) and in parallel (each file runs in its own thread using child_process or worker_threads). I believe they need to be isolated if that the source of the problem. Or you can use an -s flag, so AVA will run tests serially.