Adjust travis CI

.travis.yml

@@ -1,24 +1,41 @@
 language: php
-
 php:
   - 5.5
   - 5.6
   - 7.0
   - 7.1
   - 7.2
+  - nightly
+
+cache:
+  directories:
+    - vendor
+    - $HOME/.composer
 
 env:
+  global:
+    - DEFAULT_COMPOSER_FLAGS="--optimize-autoloader --no-interaction --no-progress"
   matrix:
     - PREFER_LOWEST="--prefer-lowest"
     - PREFER_LOWEST=""
-    fast_finish: true
-    allow_failures:
-      - php: nightly
 
 before_script:
-  - travis_retry composer self-update
+  - composer global show hirak/prestissimo -q || travis_retry composer global require $DEFAULT_COMPOSER_FLAGS hirak/prestissimo
   - travis_retry composer update --no-interaction --prefer-source $PREFER_LOWEST
   - travis_retry phpenv rehash
 
+stages:
+  - Static Code Analysis
+  - Test
+
+jobs:
+  include:
+    - stage: Static Code Analysis
+      php: 7.2
+      script:
+        - vendor/bin/php-cs-fixer fix -v --dry-run
+  allow_failures:
+    - php: nightly
+
 script:
-  - ./vendor/bin/phpunit --coverage-text --coverage-clover=coverage.clover
+  - vendor/bin/phpunit