Fix proxy task to work with https connections.

[Xevi]

Done

Server target as string instead of options Object (http-proxy defines the target as a string here) Add a getTargetUrl utility on the utils lib to get the target url based on the proxy options. Set the headers host explicitly on proxy creation to avoid host mismatches between local server and proxy. Add tests for getTargetUrl utility.

[ruiaraujo]

Thanks for the fixes and for the tests.

[Xevi]

you are welcome :)