Use ES5 instead of ES6 for target

[binarykitchen]

Including your npm package in other projects without babelification can break.

For example function findStatus(val, { useSTD3ASCIIRules }) { breaks on IE11.

See https://stackoverflow.com/questions/29738381/how-to-publish-a-module-written-in-es6-to-npm

[TimothyGu]

We do not support old browsers or even old Node.js runtimes:

https://github.com/Sebmaster/tr46.js/blob/8b4b13895dec235dde3a7aaf76572ffee70b3332/package.json#L4-L6

[gfx]

@TimothyGu Can you add it to README.md? I have fatal errors on IE11 (via whatwg-url) and I have to get it of this module.