add travis ci config

Author: cs-eliseev

.travis.yml

@@ -0,0 +1,15 @@
+language: php
+
+sudo: false
+
+matrix:
+  include:
+    - php: 7.1
+    - php: 7.2
+    - php: 7.3
+
+before_script:
+  - composer install
+
+script:
+  - phpunit