Update composer dependencies

Author: Jamie Snape

composer.json

@@ -15,7 +15,7 @@
         "ext-json": "*",
         "erusev/parsedown-extra": "~0.7",
         "francodacosta/phmagick": "0.4.*@dev",
-        "intervention/image": "~2.2",
+        "intervention/image": "~2.3",
         "ircmaxell/random-lib": "~1.1",
         "leafo/scssphp": "~0.1",
         "maennchen/zipstream-php": "~0.3",
@@ -28,15 +28,15 @@
     "require-dev": {
         "ext-curl": "*",
         "ext-xdebug": "*",
-        "fabpot/php-cs-fixer": "~1.8",
+        "fabpot/php-cs-fixer": "~1.10",
         "jokkedk/zfdebug": "~1.6",
         "phpcheckstyle/phpcheckstyle": "V0.14.1",
-        "phpunit/dbunit": "~1.3",
+        "phpunit/dbunit": "~1.4",
         "phpunit/phpcov": "~2.0",
-        "phpunit/phpunit": "~4.6",
+        "phpunit/phpunit": "~4.8",
         "satooshi/php-coveralls": "~0.6",
-        "sensiolabs/security-checker": "~2.0",
-        "symfony/console": "~2.6"
+        "sensiolabs/security-checker": "~3.0",
+        "symfony/console": "~2.7"
     },
     "suggest": {
         "ext-fileinfo": "*",