Modify implicit_wait timeout to a sane default value.

Some background: http://stackoverflow.com/questions/8852977/how-does-uiautomation-determine-whether-a-uiaelement-isvisible

If the implicit wait timeout is zero, some slower situations will not return the proper elements (returning an empty list usually). A user can override this using implicit_wait() but I think we should have a defualt that does something good by default. 

In this case, we can support the json remote wire protocol by having the function to change the implicit_wait, but we can also do the right thing by our users and have it be non-zero so it works in the majority of cases out of the box. 

I wish I had more info but UIAutomation is just poorly doc'd and I can't look at the code.