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.
I'm open to having a default value with an optional param if it improves readability or maintenance. What I don't want is to be doing a million checks for things that we should assume to be true (or blow up if not).