feature #405 Upgraded the application to Symfony 3.2.0 (javiereguiluz)

This PR was squashed before being merged into the master branch (closes #405).

Discussion
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Upgraded the application to Symfony 3.2.0

Commits
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13b1eb8 Upgraded the application to Symfony 3.2.0

Author: javiereguiluz

composer.json

@@ -23,9 +23,9 @@
         "sensio/framework-extra-bundle"        : "^3.0",
         "symfony/monolog-bundle"               : "^2.8",
         "symfony/swiftmailer-bundle"           : "^2.3",
-        "symfony/symfony"                      : "^3.2-beta1",
+        "symfony/symfony"                      : "^3.2",
         "twig/extensions"                      : "^1.3",
-        "twig/twig"                            : "^1.27",
+        "twig/twig"                            : "^1.28",
         "white-october/pagerfanta-bundle"      : "^1.0"
     },
     "require-dev": {