Use dev-streaming-multipart
Use dev-streaming-multipart

Now we can use `dev-streaming-multipart` instead of `dev-master#cd15204bd15d106d7832c680e4fb0ca0ce2f5e30`
See https://github.com/reactphp/http/issues/60#issuecomment-241349924
php-pm/php-pm,andig/php-pm,php-pm/php-pm