`client.setText` no longer calls into Flash

Fixes #295.

**Why This Works:**
This works because the text is not needed until the `copy` event rolls around.  When the `copy` event is emitted into JavaScript, it returns the entire set of contents from `_clipData` to Flash component.  As such, there is no need to forcibly call into Flash every time we want to store the new pending text. Removing this functionality eliminates the race condition described in #295 as well as reducing the API surface area of the Flash object. Win-win! :muscle: