BlobBuilder is DEPRECATED and doesn't work in FF 20

BlobBuilder is deprecated and shouldn't be used. It also doesn't work with FF 20, so I replaced it with Blob constructor which does same thing and is supported by majority of browsers. I tested it with FF 20, Chrome 24, Opera 12.12 and it works even in IE 10! (all tests on Windows)

For more information take look at Mozilla docs [Blob](https://developer.mozilla.org/en-US/docs/DOM/Blob) and [BlobBuilder](https://developer.mozilla.org/en-US/docs/DOM/BlobBuilder)

From docs:
> **Note**: The BlobBuilder interface has been deprecated in favor of the newly introduced Blob constructor.

> **Note**: Some browsers offer BlobBuilder, which lets you iteratively append data to a blob, then retrieve the completed blob when you're ready to use it for something. However, BlobBuilder is not available in every browsers and all BlobBuilder implementations have vendor prefixes. And it is deprecated in favor of the Blob constructor. You should use Blob constructor whenever possible.