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.
sendKeys is different from replaceValue. iOS has a setValue method that can be invoked on an element id. In Ruby it looks something like this

> au.getElement('#{elementId}').setValue('#{value}');)