Upgrade squizlabs/php_codesniffer. Fixes #66

Author: davidbarratt

composer.json

@@ -18,7 +18,7 @@
     },
     "require-dev": {
         "phpunit/phpunit": "^5.0 || ^4.8.10",
-        "squizlabs/php_codesniffer": "^2.3"
+        "squizlabs/php_codesniffer": "^3.5"
     },
     "autoload": {
         "psr-4": {