Resolved Symfony 3.x deprecation warnings (#15)

* Fixed error in composer.json resulting in incompatibility with Symfony 3.x

* Resolved Symfony 3.1 deprecation warnings

Author: Jan Petersen

src/Resources/config/services.yml

@@ -5,14 +5,14 @@ parameters:
 
 services:
     caxy.html_diff.config:
-        class: %caxy.html_diff.config.class%
-        factory: [%caxy.html_diff.config.class%, create]
+        class: "%caxy.html_diff.config.class%"
+        factory: ["%caxy.html_diff.config.class%", create]
     caxy.html_diff:
-        class: %caxy.html_diff.class%
+        class: "%caxy.html_diff.class%"
         calls:
             - [setConfig, ["@caxy.html_diff.config"]]
     caxy.twig.html_diff_extension:
-        class: %caxy.twig.html_diff_extension.class%
+        class: "%caxy.twig.html_diff_extension.class%"
         arguments: ["@service_container"]
         tags:
             - { name: twig.extension }