Move chef/ohai dep into a chef group so it can be excluded

Author: ramereth

Gemfile

@@ -16,12 +16,14 @@ group :development, :test do
   gem "rspec", "~> 3.0"
 end
 
-if ENV["GEMFILE_MOD"]
-  puts "GEMFILE_MOD: #{ENV["GEMFILE_MOD"]}"
-  instance_eval(ENV["GEMFILE_MOD"])
-else
-  gem "chef", "~> 18.6"
-  gem "ohai", "~> 18.0"
+group :chef do
+  if ENV["GEMFILE_MOD"]
+    puts "GEMFILE_MOD: #{ENV['GEMFILE_MOD']}"
+    instance_eval(ENV["GEMFILE_MOD"])
+  else
+    gem "chef", "~> 18.6"
+    gem "ohai", "~> 18.0"
+  end
 end
 
 group :debug do