Use request for better proxy support

Request has better built in support for those of use behind corporate proxies. Currently running the task behind a proxy that requires authentication results in various errors (EOTNOTFOUND, EDTIMEDOUTs). After this, those that set the http_proxy environment variable should correctly download the Modernizr files.

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The JSHint stuff is because the tests where failing when I first cloned and I wanted it to be green :wink: I can remove the JSHint commit if you prefer and submit it separately.