fix IE8 parse/runtime issues

This PR is rebased https://github.com/ded/reqwest/pull/155. I removed `reqwest.js` and `reqwest.min.js` as you requested in https://github.com/ded/reqwest/pull/158#issuecomment-58060901

I can not just amend previous PR, because that commit is used in production `package.json`.

@ded @drzhbe check it out