Cleanup nav styles

* Use `display: inline` to avoid 4px spacing
* Remove left padding from first element, right padding from last
Add backbone.js and update underscore.js
Remove ember
Add jquery.pjax
Add backbone-support and js-routes
Disable root elements for JSON array responses
Switch to cookies.js

Defaults `path` to `'/'` where cookie.js does not. Makes the default
settings on the client match those on the server.
Switch delivery search to be server-rendered
Port new delivery page to server-rendered/Backbone

* Always include all attributes in `UserSerializer`
* Add `Besko.Collections.Recipients` for querying recipients in
  autocomplete
* Port ember autocomplete input to backbone. Is configured by specifying
  the Backbone collection to use for querying and triggers a `select`
  event when picking a result. Requires the markup to be pre-rendered.
* Redirect to the page for the delivery after creation.
* Cleanup/update `ReceiptsHelper`
* Small modifications to tests to update them for the new markup
Remove now-unused `DeliverySerializer`
Cleanup `before_create` callback on `Delivery`

Use `Time.zone.now.to_date` over `Date.today` so timezone is taken into
account.
Don't apply button styles to all buttons by default
Remove now-unused `yield :bootstrap`