HTTPS support

I needed HTTPS for [FUDS](https://github.com/jcaraballo/fuds), so I tried adding it O:-)

It's not as neat as the rest

    https("src/test/certs/keystore-testing.jks", "password")(GET(server.url + expected))

because I like being able to pass the key store explicitly.

If you want to add HTTPS... Yay!

\o/

（＾ｖ＾）

--Joaquín