laravel 5.6 support

.travis.yml

@@ -9,22 +9,22 @@ notifications:
     email:
         on_success: never
         on_failure: always
-
 php:
   - 7.0
   - 7.1
   - 7.2
 
 env:
-  - LARAVEL_VERSION=5.5.*
+  matrix:
+    - COMPOSER_FLAGS="--prefer-lowest"
+    - COMPOSER_FLAGS=""
 
 before_install:
   - travis_retry composer self-update --stable -n
   - composer validate --no-check-all --strict
-  - composer require "laravel/framework:${LARAVEL_VERSION}" --no-update -n
 
 install:
-  - travis_retry composer install --no-suggest --prefer-dist -n -o
+  - travis_retry composer update --prefer-source $COMPOSER_FLAGS
   - composer require satooshi/php-coveralls --dev
 
 script:

composer.json

@@ -28,15 +28,15 @@
     ]
   },
   "require": {
-    "illuminate/container": "~5.5.0",
-    "illuminate/database": "~5.5.0",
-    "illuminate/redis": "~5.5.0",
-    "illuminate/support": "~5.5.0"
+    "illuminate/container": "~5.5.0|~5.6.0",
+    "illuminate/database": "~5.5.0|~5.6.0",
+    "illuminate/redis": "~5.5.0|~5.6.0",
+    "illuminate/support": "~5.5.0|~5.6.0"
   },
   "require-dev": {
-    "orchestra/testbench": "~3.5.0",
+    "orchestra/testbench": "~3.5.0|~3.6.0",
     "phpmd/phpmd": "^2.6",
-    "phpunit/phpunit": "~6.0",
+    "phpunit/phpunit": "~6.0|~7.0",
     "predis/predis": "^1.1",
     "sebastian/phpcpd": "^3.0",
     "squizlabs/php_codesniffer": "^2.7"