Fix exceptions with jQuery.noConflict()

When using `Turbolinks` with `jQuery` and other libraries that depend on the `$` function/object there are exceptions due to jQuery not being aliased to `$`.

One solution might be putting the
``` js
jQuery.noConflict();
```
call right after loading `turbolinks` in the `application.js` manifest, but it's a bit arcane and unclean.