Install compatible versions of phpunit dependencies

sabberworm · sabberworm · commit ecda1feeb4e5 · 2017-05-31T10:51:20.000+02:00
instead of using lockfile

This fixes travis builds for ancient versions of PHP (5.3 and 5.4)
diff --git a/.travis.yml b/.travis.yml
@@ -9,7 +9,7 @@ php:
     - "nightly"
     - hhvm
 dist: trusty
-before_script: composer install
+before_script: rm composer.lock && composer install
 script: ./vendor/phpunit/phpunit/phpunit
 sudo: false
 
