Refactor examples for default suite tests into shared examples
Add integration tests for slave recipe using mesosphere

Actually needed a few changes to both `slave` and `mesosphere` recipes:

* Install `libcurl3` package in `mesosphere` recipe as it was needed to
get dpkg to actually install mesos, otherwise it would complain about
dependency requirements that weren't met.
* Use Chef::Application.fatal! as Chef::Log.fatal! doesn't exist in
newer versions of chef, though I think Chef::Application.fatal! exist
in older versions of chef. I'm not sure about this at all.