Added replace parameter for setText

Requires https://github.com/admc/wd/pull/333 to be pulled first.

I also want to create a test for this in keyboard-specs.js but I can add that in another pull. 

Tested with the wd.js change and it works for me.
why should replace be optional?

this is an internal API only we are using. we can enforce whatever requirements on it we want; the decision doesn't impact the user at all.