Update composer and travis dependencies

Author: rubenvanassche

.travis.yml

@@ -15,9 +15,9 @@ matrix:
         - php: 7.2
           env: LARAVEL='5.8.*' TESTBENCH='3.8.*' COMPOSER_FLAGS='--prefer-stable'
         - php: 7.2
-          env: LARAVEL='6.0.*' TESTBENCH='4.0.*' COMPOSER_FLAGS='--prefer-lowest'
+          env: LARAVEL='6.*' TESTBENCH='4.*' COMPOSER_FLAGS='--prefer-lowest'
         - php: 7.2
-          env: LARAVEL='6.0.*' TESTBENCH='4.0.*' COMPOSER_FLAGS='--prefer-stable'
+          env: LARAVEL='6.*' TESTBENCH='4.*' COMPOSER_FLAGS='--prefer-stable'
         - php: 7.3
           env: LARAVEL='5.8.*' TESTBENCH='3.8.*' COMPOSER_FLAGS='--prefer-lowest'
         - php: 7.3

composer.json

@@ -32,7 +32,7 @@
     },
     "require-dev": {
         "phpunit/phpunit": "^8.0",
-        "orchestra/testbench": "~3.8.0|^4.0.0"
+        "orchestra/testbench": "~3.8.0|^4.0"
     },
     "autoload": {
         "psr-4": {