Add travis CI

Signed-off-by: Jack Cherng <jfcherng@gmail.com>

Author: jfcherng

.travis.yml

@@ -0,0 +1,21 @@
+language: php
+
+php:
+  - 7.1
+  - 7.2
+  - 7.3
+
+cache:
+  directories:
+    - $HOME/.composer/cache
+
+before_install:
+  - pecl install -f ast
+
+install:
+  - rm -f composer.lock  # temporary fix for PHPUnit 8
+  - composer install --prefer-dist --no-progress
+
+script:
+  - composer analyze
+  - composer test