Added, and configured, php-cs-fixer with a Makefile to invoke fix and test

.php_cs

@@ -0,0 +1,14 @@
+<?php
+
+$finder = PhpCsFixer\Finder::create()
+    ->in(__DIR__ . '/src')
+    ->in(__DIR__ . '/tests')
+;
+
+return PhpCsFixer\Config::create()
+    ->setUsingCache(false)
+    ->setRules([
+        '@PSR2' => true,
+    ])
+    ->setFinder($finder)
+;

.travis.yml

@@ -10,5 +10,8 @@ before_install:
 install:
     - travis_retry composer install --no-interaction --prefer-source
 
+before_script:
+    - php -v
+
 script:
-    - composer test
+    - make all

Makefile

@@ -0,0 +1,12 @@
+THIS := $(realpath $(lastword $(MAKEFILE_LIST)))
+HERE := $(shell dirname $(THIS))
+
+.PHONY: all fix test
+
+all: fix test
+
+fix:
+	php $(HERE)/vendor/bin/php-cs-fixer fix --config=$(HERE)/.php_cs
+
+test:
+	php $(HERE)/vendor/bin/phpunit --configuration $(HERE)/phpunit.xml

composer.json

@@ -5,7 +5,8 @@
   "require": {
     "guzzlehttp/guzzle": "^6.2.2",
     "php": ">=7.0.0",
-    "psr/http-message": "~1.0"
+    "psr/http-message": "~1.0",
+    "friendsofphp/php-cs-fixer": "^2.6"
   },
   "require-dev": {
     "phpunit/phpunit": "5.7.5",
@@ -22,8 +23,5 @@
     "psr-4": {
       "Cloudflare\\API\\": "src/"
     }
-  },
-  "scripts": {
-    "test": "phpunit"
   }
 }