add jshint to `make test`

* add a lint target to the Makefile that runs jshint
* fix all jshint errors from the default config
* have the make test target run the lint target
Yeah... I think you're right.  We want a `(!result)` here.  It was a bit hard to tell what you're trying to do with you always checking against `null` specifically, but I guess that's the point of the jshint check.