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.
> In this case, if the replace param is not there, it's a programming error on our part rather than anything the user could do

replace should be optional and then it's not a programming error if we're omitting it.