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.
> It's a good practice to always suspect your data, especially when dealing with types or data structures generated dynamically from strings, e.g. json, objects deserialized from xml, etc.

I agree, kind of. I think it's good practice to always suspect your data *in one place*, but to assume it's been sanitized everywhere else. Otherwise you end up with this waterfall of vacuous checks.

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, so I'm inclined to not check and let it throw/crash to let us know there's a bug we need to fix