Merge "Start using the Assert helper class for checking parameters."

diff --combined composer.json
index bc0dacb,1495198..da6d334
--- 1/composer.json
--- 2/composer.json
+++ b/composer.json
@@@ -20,10 -20,11 +20,11 @@@
                "ext-iconv": "*",
                "leafo/lessphp": "0.5.0",
                "liuggio/statsd-php-client": "1.0.12",
 -              "oojs/oojs-ui": "0.11.1",
 +              "oojs/oojs-ui": "0.11.2",
                "php": ">=5.3.3",
                "psr/log": "1.0.0",
                "wikimedia/cdb": "1.0.1",
+               "wikimedia/assert": "0.2.2",
                "wikimedia/composer-merge-plugin": "1.0.0",
                "wikimedia/utfnormal": "1.0.2",
                "zordius/lightncandy": "0.18"