Don't fire ajaxyness if "data-remote"="false"

Hi all,

It seems sort of weird that link/form/btn which has `"data-remote"="false"` is treated as it had `"data-remote"="true"` (or just `"data-remote"`). Taking into account that we regularly do use ujs functionality with rails helpers, almost everyone passes a value to the `data-remote` attribute.

It will be useful in such cases as following (simplified example):
```ruby
- @links.each do |link|
  = link_to link.name, link.href, data: { remote: link.remote? }
```

Despite the fact the case I stumbled upon is quite rare, having ajax proceeding with `"data-remote"="false"` seems weird anyway.