feature to have the option to change the key of the wsdl

[Lucas-Mondini]

I was having a problem with a company, that the wsdl was returning the wrong data to the soapclient; but despite i knew the expected data, I can't change by the code.
So I made a small change that allow me to change the XML key before send to the server
I just have to pass an object with the key value that I want to change, and the value that I want that this key have

        const options = { 
            overrideElementKey: {
                oldKeyOnTheXML: "NewKeyOnTheXML"
            }
        }

[jsdevel]

please document this in the README

[smokhov]

@w666 -- is it only the README change that is required that's holding up this?

[w666]

Also needs a test. I added this one to my todo list.