Use custom payload format to transfer jobs

This makes the plugin incompatible with Laravel 5.7 as they changed
the internal method signatures. The queue class cannot be compatible
with both at the same time.

Author: mzur

composer.json

@@ -1,6 +1,6 @@
 {
     "name": "biigle/laravel-remote-queue",
-    "description": "Submit jobs to another Laravel or Lumen instance.",
+    "description": "Submit jobs to and receive jobs from other Laravel or Lumen instances.",
     "type": "library",
     "authors": [
         {
@@ -10,10 +10,10 @@
     ],
     "require": {
         "guzzlehttp/guzzle": "~6.0",
-        "illuminate/queue": "^5.5",
-        "illuminate/support": "^5.5",
-        "illuminate/contracts": "^5.5",
-        "illuminate/routing": "^5.5"
+        "illuminate/queue": "5.5.*",
+        "illuminate/support": "5.5.*",
+        "illuminate/contracts": "5.5.*",
+        "illuminate/routing": "5.5.*"
     },
     "autoload": {
         "psr-4": {
@@ -36,7 +36,7 @@
         }
     },
     "require-dev": {
-        "laravel/laravel": "^5.5",
+        "laravel/laravel": "5.5.*",
         "phpunit/phpunit": "^7.4",
         "mockery/mockery": "^1.2"
     }