Remove composer lock on travis build to make sure all PHP versions are tested.

IvanChepurnyi · IvanChepurnyi · commit e5f30005e42b · 2018-05-22T23:01:31.000+02:00
diff --git a/.travis.yml b/.travis.yml
@@ -3,5 +3,5 @@ php:
   - '7.1'
   - '7.2'
   - nightly
-before_script: composer install
+before_script: rm composer.lock && composer install
 script: composer test
