feature #712 Upgrade to Symfony 4.0.0 release (yceruto)

This PR was merged into the master branch.

Discussion
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Upgrade to Symfony 4.0.0 release

:tada: :balloon: :birthday: :gift: :heart: :smiley:

Also updating to latest changes from recipes.

Commits
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708ba64 Upgrade to Symfony 4.0.0 release

Author: javiereguiluz

composer.json

@@ -7,7 +7,7 @@
         "php": "^7.1.3",
         "ext-pdo_sqlite": "*",
         "doctrine/doctrine-bundle": "^1.8",
-        "doctrine/doctrine-fixtures-bundle": "^2.4",
+        "doctrine/doctrine-fixtures-bundle": "^3.0",
         "erusev/parsedown": "^1.6",
         "ezyang/htmlpurifier": "^4.9",
         "sensio/framework-extra-bundle": "^5.0",
@@ -70,7 +70,6 @@
     "conflict": {
         "symfony/symfony": "*"
     },
-    "minimum-stability": "beta",
     "extra": {
         "symfony": {
             "id": "01BY8QJHBGTYRP06WQFNY99EKP",