Add support for Blob

[lpinca]

Closes #2206

[lpinca]

@kettanaito I'm still not very happy with this because, other than compatibility with the WHAWG spec, it is pretty much useless. Anyway, here it is. I also didn't run any benchmarks to see the impact on performance.

[kettanaito]

Which summarizes the entire change pretty flawlessly. I am still grateful for this consistency! Thank you!

[titanism]

Hi there @lpinca, I can't confirm exactly what's wrong here, but I did a minor version bump and this entirely broke our implementation of ws. It's sending everything over the wire as a BLOB now instead of as a Buffer it seems. Seems to be a major breaking change (e.g. we are using msgpackr under the hood to pack/unpack messages sent via websockets, and now they are throwing an error Source must be a Uint8Array or Buffer but was a Blob).

[lpinca]

@titanism are you are setting websocket.binaryType to 'blob'? Let's continue the discussion in #2239.

[nikwen]

Was just looking at the commit to make sure that upgrading ws won't break my app. Looks great overall. Just had a small suggestion. :)

[nikwen]

This seems worthwhile to pull out into a small function:

function emitError(err) {
  websocket._errorEmitted = true;
  websocket.emit('error', err);
}

Seems like these lines should always be called together. Pulling them out into a function will make it less likely that someone will forget to do so in the future.