Alternative `selectedText` implementation.

It works, in theory, with all applications. Quick and dirty hack.

A better approach would be to export a pasteboard event emitter where
the configuration script can listen waiting for items of certain to be
available. À la node it would be something like this:

pasteboard.on('string', function(item /* copied item */, app /* originating app */( {
    /* do something with item */
})

pasteboard.on('image', function(item, app) {
    /* do something with item */
})

Not sure how to do it in Windows app yet.