staging for virtualenv
Complete rewrite using libCURL and callbacks
Hoping for a more stable stream and a faster download

Things we learned: using pipes for communication with the subprecess is
not possible to decouple the chain rawdata->pipein->trans->pipeout->data
(say, in two separate threads). You need to write, wait, collect, all in
one. (though is pretty obvious i was hoping to do in a different way)