Binary files are not handled properly

[whscullin]

This library calls .toString() on all resources. If the resources is a binary file, like a PNG or font, Bad Things Happen, and the browser will disagree with the calculated hash.

[mathisonian]

Thanks @whscullin, apologies that I missed your PR - I've released v0.3.1 on npm

[whscullin]

Awesome. Thanks!