guess who finally added jshint to their setup?
adds more thorough testing

* null/undefined readme fields do not throw exceptions & cause all package prep to fail
* readmes that make marked throw are still sanitized
* readmes that aren't identified as markdown are sanitized
* readmes that are not at the top level & need promotion are sanitized
* readmes that are stored in files as not markdown are sanitized
* readmes that are stored in files as markdown are sanitized