Add unit test SimpleWalker + Travis integration

Author: Babacooll

.travis.yml

@@ -0,0 +1,8 @@
+language: php
+php:
+  - 5.6
+  - hhvm
+  - nightly
+
+before_script:
+  - composer install

composer.json

@@ -13,5 +13,8 @@
     ],
     "require": {
         "symfony/filesystem": "^3.0"
+    },
+    "require-dev": {
+        "phpunit/phpunit": "^5.2"
     }
 }