Add .travis.yml, run test

Author: socheatsok78

.travis.yml

@@ -0,0 +1,15 @@
+language: php
+
+php:
+  - 7.1
+  - 7.2
+  - 7.3
+
+dist: trusty
+
+install:
+  - composer self-update
+  - composer install
+
+script:
+  - "./vendor/bin/phpunit --coverage-text"