Add Travis checks

Author: jakubboucek

.travis.yml

@@ -0,0 +1,22 @@
+language: php
+php:
+  - 7.2
+  - 7.3
+
+before_install:
+  # turn off XDebug
+  - phpenv config-rm xdebug.ini || return 0
+
+install:
+  - travis_retry composer install --no-progress --prefer-dist
+
+script:
+  - vendor/bin/phpstan analyze --level max -c phpstan.neon src --no-interaction --no-progress
+
+sudo: false
+
+cache:
+  directories:
+    - $HOME/.composer/cache
+    - tmp
+