Use udiff format in CI

.appveyor.yml

@@ -39,4 +39,5 @@ before_test:
 test_script:
     - cd C:\projects\php-cs-fixer
     - vendor\bin\phpunit
+    - set PHP_CS_FIXER_FUTURE_MODE=1
     - php php-cs-fixer --diff --dry-run -v fix

.travis.yml

@@ -57,7 +57,7 @@ jobs:
                 - composer info -D | sort
             script:
                 - vendor/bin/phpunit || travis_terminate 1
-                - php php-cs-fixer --diff --dry-run -v fix
+                - PHP_CS_FIXER_FUTURE_MODE=1 php php-cs-fixer --diff --dry-run -v fix
 
         -
             <<: *STANDARD_TEST_JOB
@@ -93,7 +93,7 @@ jobs:
                 - php php-cs-fixer fix --rules @PHP71Migration,@PHP71Migration:risky,native_function_invocation -q || travis_terminate 1
                 - vendor/bin/phpunit || travis_terminate 1
                 - git checkout . -q
-                - php php-cs-fixer --diff --dry-run -v fix
+                - PHP_CS_FIXER_FUTURE_MODE=1 php php-cs-fixer --diff --dry-run -v fix
 
         -
             stage: Deployment

circle.yml

@@ -22,4 +22,4 @@ dependencies:
 test:
     override:
         - vendor/bin/phpunit
-        - php php-cs-fixer --diff --dry-run -v fix
+        - PHP_CS_FIXER_FUTURE_MODE=1 php php-cs-fixer --diff --dry-run -v fix