Fix newrelic testing based on upstream

Fixes #67, upstream released a new version of the newrelic meetme agent cookbook, switching to LWRPs for some pieces of functionality we were testing in chefspec. This commit moves those to serverspec tests, and also removes the extraneous testing of distros where we didn't check any differences. I also added some guards for recipes that didn't like being converged with 'demo' set to true but with nginx enabled (the demo was only working w/ apache).