Update composer with latest version.

composer.json

@@ -48,6 +48,7 @@
         "ext-xml": "*",
         "ext-json": "*",
         "ext-mbstring": "*",
+        "ext-bcmath": "*",
         "twig/twig": "2.*",
         "doctrine/orm": "^2.5.11",
         "doctrine/dbal": "~2.5",
@@ -56,8 +57,8 @@
         "doctrine/doctrine-fixtures-bundle": "^3.0",
         "doctrine/doctrine-migrations-bundle": "^1.3",
 
-        "erusev/parsedown": "^1.6",
+        "erusev/parsedown": "^1.7",
-        "ezyang/htmlpurifier": "^4.9",
+        "ezyang/htmlpurifier": "^4.10",
         "sensio/framework-extra-bundle": "^5.0",
         "sensiolabs/security-checker": "^4.1",
 
@@ -67,9 +68,9 @@
         "symfony/form": "^3.0|^4.0",
         "symfony/framework-bundle": "^3.0|^4.0",
         "symfony/monolog-bundle": "^3.1",
-        "symfony/polyfill-apcu": "^1.6",
+        "symfony/polyfill-apcu": "^1.7",
-        "symfony/security-bundle": "^3.0|^4.0",
+        "symfony/security-bundle": "^4.0",
-        "symfony/swiftmailer-bundle": "^3.1",
+        "symfony/swiftmailer-bundle": "^3.2",
         "symfony/translation": "^4.0",
         "symfony/twig-bundle": "^3.0|^4.0",
         "symfony/validator": "^3.0|^4.0",
@@ -97,12 +98,12 @@
         "sonata-project/intl-bundle": "~2.4.0",
         "sonata-project/media-bundle": "~3.0",
         "sonata-project/notification-bundle": "~3.0",
-        "sonata-project/page-bundle": "3.7.*",
+        "sonata-project/page-bundle": "~3.0",
         "sonata-project/seo-bundle": "~2.0",
         "sonata-project/sonata-composer": "dev-master",
-        "sonata-project/user-bundle": "4.x-dev",
+        "sonata-project/user-bundle": "~4.0",
 
-        "stephpy/timeline-bundle": "~2.0",
+        "stephpy/timeline-bundle": "~3.0",
         "stof/doctrine-extensions-bundle": "~1.0",
         "sunra/php-simple-html-dom-parser": "~1.5.0",
         "sylius/resource-bundle": "1.0.4",