Compatibility overhaul

[jimmywarting]

Sorry for such a big commit/change... would rather want to do smaller PR and many PR, but it often result in things taking longer for things to be accepted and merged...

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When stream, arrayBuffer and text was announced i started to look back into node-fetch to try and implement dose functionalities... And they are there now.

But node-fetch is looking into extracting out there own Blob implementation and use a third-party blob implementation instead, figured instead of creating yet another module we could use something that already exist. so i looked back into your Blob.js implementation.

If node-fetch is ever going to use your version of blob.js then there are a few things that needs to happen before we even consider it. And that is what this PR is solving.

• stream, text and arrayBuffer need to exist.
• Node is going to want to have typed arrays (this pr now use them when possible)
• text must provide the same result as response.text() and FileReader.readAsText
  • (your current version didn't) test the old and the new (this PR) in jsfiddle
• setting Symbol.toStringTag didn't work correctly when blob was undefined
• other nice things that i found while search browsers native test harness
  • 6682a51 (discard bad mimetype)
  • 5735017 (change / to : in FileNames)

closes #65 closes #66

[jimmywarting]

the new methods require promises and readableStream but I thing that is beyond the scope of blob.js They should include stream and promise polyfills themself if they need to

[eligrey]

Thank you!