Configure Redis through environment variables. Closes #805

.env.example

@@ -20,3 +20,7 @@ MAIL_USERNAME=null
 MAIL_PASSWORD=null
 MAIL_ADDRESS=null
 MAIL_NAME=null
+
+REDIS_HOST=null
+REDIS_DATABASE=null
+REDIS_PORT=null

config/database.php

@@ -124,9 +124,9 @@ return [
         'cluster' => false,
 
         'default' => [
-            'host'     => '127.0.0.1',
+            'host'     => env('REDIS_HOST', '127.0.0.1'),
-            'port'     => 6379,
+            'port'     => env('REDIS_PORT', 6379),
-            'database' => 0,
+            'database' => env('REDIS_DATABASE', 0),
         ],
 
     ],