Fix Travis CI build, which had configured composer to install newer dependencies than could be run on some tested php versions.

Author: mbaynton

.travis.yml

@@ -22,7 +22,7 @@ addons:
 env:
   global:
     - TESTS_ZEND_LDAP_ONLINE_ENABLED=true
-    - COMPOSER_ARGS="--no-interaction --ignore-platform-reqs"
+    - COMPOSER_ARGS="--no-interaction"
     - SITE_URL: https://zendframework.github.io/zend-ldap
     - GH_USER_NAME: "Matthew Weier O'Phinney"
     - GH_USER_EMAIL: matthew@weierophinney.net