Fix Laravel 6.x dependency (#139)

Author: xel1045

composer.json

@@ -15,12 +15,12 @@
     ],
     "require": {
         "php": ">=5.5.9",
-        "illuminate/contracts": "5.1.*|5.2.*|5.3.*|5.4.*|5.5.*|5.6.*|5.7.*|5.8.*|6.0.*",
-        "illuminate/filesystem": "5.1.*|5.2.*|5.3.*|5.4.*|5.5.*|5.6.*|5.7.*|5.8.*|6.0.*",
-        "illuminate/http": "5.1.*|5.2.*|5.3.*|5.4.*|5.5.*|5.6.*|5.7.*|5.8.*|6.0.*",
-        "illuminate/routing": "5.1.*|5.2.*|5.3.*|5.4.*|5.5.*|5.6.*|5.7.*|5.8.*|6.0.*",
-        "illuminate/support": "5.1.*|5.2.*|5.3.*|5.4.*|5.5.*|5.6.*|5.7.*|5.8.*|6.0.*",
-        "illuminate/view": "5.1.*|5.2.*|5.3.*|5.4.*|5.5.*|5.6.*|5.7.*|5.8.*|6.0.*",
+        "illuminate/contracts": "5.1.*|5.2.*|5.3.*|5.4.*|5.5.*|5.6.*|5.7.*|5.8.*|^6.0",
+        "illuminate/filesystem": "5.1.*|5.2.*|5.3.*|5.4.*|5.5.*|5.6.*|5.7.*|5.8.*|^6.0",
+        "illuminate/http": "5.1.*|5.2.*|5.3.*|5.4.*|5.5.*|5.6.*|5.7.*|5.8.*|^6.0",
+        "illuminate/routing": "5.1.*|5.2.*|5.3.*|5.4.*|5.5.*|5.6.*|5.7.*|5.8.*|^6.0",
+        "illuminate/support": "5.1.*|5.2.*|5.3.*|5.4.*|5.5.*|5.6.*|5.7.*|5.8.*|^6.0",
+        "illuminate/view": "5.1.*|5.2.*|5.3.*|5.4.*|5.5.*|5.6.*|5.7.*|5.8.*|^6.0",
         "mrclay/minify": "^2.2"
     },
     "require-dev": {