Add travis yaml file + move test folder to _build

Author: joeke

.travis.yml

@@ -0,0 +1,16 @@
+language: php
+script: "phpunit -c _build/test/phpunit.xml"
+
+# Set php versions
+php:
+  - 5.3
+  - 5.4
+  - 5.5
+  - 5.6
+  - 7.0
+  - 7.1
+  - hhvm
+
+matrix:
+  allow_failures:
+    - php: hhvm