Laravel 6.0 Support (#28)

* Delete version constraint

* Update composer.json

* Only 6.0

Author: kawax

.travis.yml

@@ -1,7 +1,6 @@
 language: php
 
 php:
-  - 7.1
   - 7.2
   - 7.3
 

composer.json

@@ -18,21 +18,19 @@
         }
     ],
     "require": {
-        "php": ">=7.1.2",
+        "php": "^7.2",
         "ext-json": "*",
-        "guzzlehttp/guzzle": "~6.3",
-        "illuminate/notifications": "^5.6",
-        "illuminate/support": "^5.6",
-        "illuminate/queue": "^5.6",
-        "illuminate/console": "^5.6",
+        "guzzlehttp/guzzle": "^6.3",
+        "illuminate/notifications": "^6.0",
+        "illuminate/support": "^6.0",
+        "illuminate/queue": "^6.0",
+        "illuminate/console": "^6.0",
         "textalk/websocket": "^1.2"
     },
     "require-dev": {
         "mockery/mockery": "^1.0",
-        "orchestra/testbench": "^3.6",
-        "laravel/framework": "^5.6",
-        "phpunit/phpunit": "7.*",
-        "orchestra/database": "3.8.x-dev"
+        "orchestra/testbench": "^4.0",
+        "phpunit/phpunit": "^8.0"
     },
     "autoload": {
         "psr-4": {