use call to run wget and curl

When wget and/or curl is wrapped in a .bat or .cmd file as is done by [Chocolatey](http://chocolatey.org) then you have to use call to be able to execute them. If you don't do this then the bat file hangs and when you put echo on you get the error "The system cannot find the batch label specified". Using call to run executables works without issues on at least Windows 7.