Remove Array.prototype.map polyfill

[tkrotoff]

Array.prototype.map polyfill should be removed. It should be done instead by the user (the application that is using iban.js).
And of course bump major version number and add some documentation about it inside README.md (in a section like "Supported browsers", example: https://reactjs.org/docs/react-dom.html#browser-support).

(btw Array.prototype.map is implemented by all browsers and IE >= 9)

[zyv]

There is already an open PR #41 for this one, please vote there :)