Execute PHP Parallel Linter on Travis

.travis.yml

 
 
 script:
+  - sh -c "if [ '$TC' = 'syntax' ]; then composer install && lib/composer/bin/parallel-lint --exclude lib/composer/jakub-onderka/ --exclude 3rdparty .; fi"
   - sh -c "if [ '$TEST_DAV' != '1' ]; then echo \"Not testing DAV\"; fi"
   - sh -c "if [ '$TEST_DAV' = '1' ]; then echo \"Testing DAV\"; fi"
 
       env: DB=sqlite;TC=carddav
     - php: 5.4
       env: DB=sqlite;TC=caldav
+    - php: 5.4
+      env: DB=sqlite;TC=syntax
+    - php: 5.5
+      env: DB=sqlite;TC=syntax
+    - php: 5.6
+      env: DB=sqlite;TC=syntax
+    - php: 7.0
+      env: DB=sqlite;TC=syntax
 
   fast_finish: true

composer.json

     },
     "autoload" : {
         "psr-4": {"OC\\": "lib/private"}
+    },
+    "require-dev": {
+        "jakub-onderka/php-parallel-lint": "^0.9.2",
+        "jakub-onderka/php-console-highlighter": "^0.3.2"
     }
 }