Uses Array.from() which is not supported in IE

UMbed is currently using `Array.from()` which is not supported in IE, so causes errors. There is [a polyfill](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/from#Polyfill), though it's a rather large implementation, so I'm not sure whether it's best to work around it or use the polyfill.