Remove some annoying CoreText spam [#83]
Still include poltergeist on other platforms [#83]
More forgiving os-detection [#83]

I'm seeing the coretext warnings on darwin13.1, so just absorb warnings
on all OSX platforms.
Merge branch 'master' into silence-mavericks-warnings

Conflicts:
	spec/spec_helper.rb
Merge pull request #84 from AndrewLorente/silence-mavericks-warnings

Remove some annoying CoreText spam [#83]