This PR was merged into the 2.1.x-dev branch.

Discussion
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Error using EsiFragment with provider and twig functions

Trying to use twig functions "controller" and "render_esi" like [Symfony esi reference](http://symfony.com/doc/current/http_cache/esi.html) , i've noticed the following error:
An exception has been thrown during the rendering of a template ("You must use a URI when using the ESI rendering strategy or set a URL signer.").

It's the lack of a UriSigner on the constructor.

Commits
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c6bbc48b Update HttpFragmentServiceProvider.php