moved the modernizr placeholder fix from go-local-subscriptions to to-ui

related to https://github.com/GigaOM/go-local-subscriptions/pull/1
actually come to think of it, on IE10+ this code will not be invoked anyways, because [if Modernizr has placeholder, then we don't even bother run this workaround](https://github.com/GigaOM/go-ui/blob/master/components/js/lib/modernizr.placeholder-fix.js#L8). So I'm inclined to just take this out.