@btm I'm not really sure the best way forward for this. I've never had to write tests around code that may or may not have dependencies installed, but I *really* wanted to test both cases.

Originally I was going to leave it out, but then I saw that `sigar` was being installed in the `:development` bundle group in order to test another plugin.

I'll take it out for now, but it means that in order to test the two code branches, you'll need to:

* Run `bundle exec rspec` to run the tests that check code paths when `ipaddr_extensions` is not present
* Manually run `gem install ipaddr_extensions`, then run `rspec` outside of Bundler to run the tests that check code paths when `ipaddr_extensions` *is* installed.