Don't set XHR content-type if postData is FormData. (#414)
Don't set XHR content-type if postData is FormData. (#414)

Browser will automatically set mime type and boundary.

youtube/spfjs,youtube/spfjs,nicksay/spfjs,nicksay/spfjs,nicksay/spfjs,youtube/spfjs,nicksay/spfjs,youtube/spfjs,youtube/spfjs,nicksay/spfjs