v5.0.0

• Update Promise polyfill to es6-promise@4.0.3.

This introduces a breaking change from es6-promise, which in previous versions would patch the global instance of Promise with its polyfill if it did not exist. Because of this, es6-promisify may also have patched your global Promise when it required es6-promise. As of es6-promise@4.0.0, the global scope is no longer patched, which means this library no longer patches it either.