Added Sauce Labs auth to travis config.
Set up Grunt + Mocha for browser testing.

Adapted from https://saucelabs.com/javascript/mocha-js
Added Sauce Labs badge to readme.
Added Encoding API polyfill to browser test.

Also switched to tag URLs for downloaded JS files.
Added Promise polyfill for IE.
Implemented workaround for IE 10, 11.

They don't support ArrayBuffer.prototype.slice().
Removed IE 8, 9, added mobile browser tests.

Also tried to fix Chrome 37 not being tested.
Re-implemented Node tests in Grunt.
Merge branch 'grunt-sauce'