Adding IEDriver to download and fixing install bug in windows

Hey man,

Im using your package in npm, but i need that your package download the iedriver as well.
Then I included it in your project.
If you can accept i will be grateful using your package, otherwise i will have to use another package that provide me a iedriver as well.

Other thing i didi was to fix a problem when run install.js in windows, because there is no chmod in windows.