Support proxies

[fenix-hub]

# Configure with authentication:
Unirest.config().proxy("proxy.com", 7777, "username", "password1!");

# or without
Unirest.config().proxy("proxy.com", 7777);

# or pass it in the request. This will override any proxy done in the config
# currently only unauthenticated proxies work
Unirest.get(MockServer.GET)
.proxy("proxy.com", 7777)
.asString();