getting rid of core-js.md

1. At start of n-ui/main.js have

window.ftNextDummySymbol = function (){return {iterator: {}}};

This will mean any typeofs called before polyfill shave loaded don't error. Safe to do as any typeof calls looking for Symbol in our application before polyfills have loaded shodul be made to fail anyway

2. Create an npm component, which has two files

• assume-symbol/symbol contains

Object.defineProperty(module.exports, 'default', {
   get: function () {
   	return window.Symbol || window.ftNextDummySymbol
   }
})

• `assume-symbol/iteratortains

Object.defineProperty(module.exports, 'default', {
   get: function () {
   	return window.Symbol.iterator || window.ftNextDummySymbol.iterator
   }
})

These will always give access to Symbol if available

3. Add some webpack aliases

  {
    'core-js/library/fn/symbol/iterator': 'assume-symbol/iterator',
    'core-js/library/fn/symbol': 'assume-symbol/symbol'
  }

4. Unexclude Symbol etc from polyfill.io
5. Build without polyfills
6. Fix whatever the hell is up with header!!!! Implement Array[@@iterator], NodeList[@@iterator], String[@@iterator] in polyfill.io
7. Shazzam!

https://github.com/Financial-Times/babel-polyfill-silencer/tree/master