Added codesniffer with PSR2 rules

Author: boesing

composer.json

@@ -36,7 +36,8 @@
         }
     },
     "require-dev": {
-        "phpunit/phpunit": "^7.3"
+        "phpunit/phpunit": "^5.7.27 || ^6.5.8 || ^7.1.2",
+        "squizlabs/php_codesniffer": "^3.3"
     },
     "archive": {
         "exclude": [
@@ -46,5 +47,16 @@
     },
     "config": {
         "sort-packages": true
+    },
+    "scripts": {
+        "check": [
+            "@cs-check",
+            "@test"
+        ],
+        "cs-check": "phpcs",
+        "cs-fix": "phpcbf",
+        "test": "phpunit --colors=always",
+        "test-coverage": "phpunit --colors=always --coverage-clover clover.xml",
+        "upload-coverage": "coveralls -v"
     }
 }