Updated curl flags

The url redirects. Providing -L tells curl to follow the redirect.
       -L, --location
              (HTTP/HTTPS)  If  the server reports that the requested page has moved to a dif-
              ferent location (indicated with a Location: header and  a  3XX  response  code),
              this  option  will make curl redo the request on the new place.
Merge pull request #40 from Doerge/patch-1

Updated curl flags in README.