[core] Move XML/JSON code up out of core

Rather than embedding XML and JSON support within fog-core, this is the
start of extracting them to exist alongside core.

That will move the responsibility to each provider to declare if they want
XML or JSON services.

Goal being as we move towards a modular fog this allows providers to
require core and either JSON or XML gems and not pick up dependencies
only required by the other.

lib/fog/aws/credential_fetcher.rb

@@ -1,4 +1,5 @@
-require 'fog/core/json'
+require "fog/json"
+
 module Fog
   module AWS
     module CredentialFetcher
@@ -61,4 +62,3 @@ module Fog
     end
   end
 end
-

lib/fog/core.rb

@@ -19,11 +19,9 @@ require 'fog/core/current_machine'
 require 'fog/core/deprecation'
 require 'fog/core/errors'
 require 'fog/core/hmac'
-require 'fog/core/json'
 require 'fog/core/logger'
 require 'fog/core/model'
 require 'fog/core/mock'
-require 'fog/core/parser' # FIXME: would be better to only load when nokogiri is required
 require 'fog/core/provider'
 require 'fog/core/service'
 require 'fog/core/ssh'
@@ -32,6 +30,11 @@ require 'fog/core/time'
 require 'fog/core/timeout'
 require 'fog/core/wait_for'
 
+# data exchange specific (to be extracted and used on a per provider basis)
+require 'fog/xml'
+require 'fog/json'
+
+
 # service wrappers
 require 'fog/compute'
 require 'fog/identity'

lib/fog/core/parser.rb

@@ -1,4 +1,4 @@
-require 'nokogiri'
+require "nokogiri"
 
 module Fog
   module Parsers

lib/fog/json.rb

@@ -1,6 +1,18 @@
-require 'multi_json'
+require "multi_json"
 
 module Fog
+
+  # @note Extracting JSON components out of core is a work in progress.
+  #
+  # The {JSON} module includes functionality that is common between APIs using
+  # JSON to send and receive data.
+  #
+  # The intent is to provide common code for provider APIs using JSON but not
+  # require it for those using XML.
+  #
+  # @todo Add +require "fog/json" and/or +include Fog::JSON+ to providers using
+  #   its services
+  #
   module JSON
 
     def self.sanitize(data)
@@ -28,6 +40,5 @@ module Fog
     def self.decode(obj)
       MultiJson.decode(obj)
     end
-
   end
 end

lib/fog/xml.rb

@@ -0,0 +1,19 @@
+require "nokogiri"
+require "fog/core/parser"
+
+module Fog
+
+  # @note Extracting XML components out of core is a work in progress.
+  #
+  # The {XML} module includes functionality that is common between APIs using
+  # XML to send and receive data.
+  #
+  # The intent is to provide common code for provider APIs using XML but not
+  # require it for those using JSON.
+  #
+  # @todo Add +require "fog/xml"+ and/or +include Fog::XML+ to providers using
+  #   its services
+  #
+  module XML
+  end
+end