drop gump requirement.. it's almost dead

Author: ikkez

Diff for: composer.json

@@ -4,9 +4,6 @@
     "keywords": ["F3","fatfree","validation","cortex","GUMP","model"],
     "homepage": "https://github.com/ikkez/f3-validation-engine",
     "license": "GPL-3.0",
-    "require": {
-        "wixel/gump": "^1.5"
-    },
     "autoload": {
         "classmap": ["src/"]
     }