Use stable version and allow backwards compatibility

Author: mpociot

composer.json

@@ -13,16 +13,14 @@
     ],
     "require": {
         "php": ">=5.6.4",
-        "illuminate/notifications": "^5.3@dev",
-        "illuminate/support": "^5.3@dev",
-        "illuminate/events": "^5.3@dev",
-        "illuminate/database": "^5.3@dev",
+        "illuminate/notifications": "5.3.*",
+        "illuminate/support": "5.1.*|5.2.*|5.3.*",
         "minishlink/web-push": "^1.1"
     },
     "require-dev": {
         "mockery/mockery": "^0.9.5",
         "phpunit/phpunit": "4.*",
-        "orchestra/testbench": "^3.3@dev"
+        "orchestra/testbench": "3.3.*"
     },
     "autoload": {
         "psr-4": {
@@ -37,7 +35,6 @@
     "config": {
         "sort-packages": true
     },
-    "minimum-stability": "dev",
     "prefer-stable": true,
     "scripts": {
         "test": "vendor/bin/phpunit"