fixed broken build after multi_json upgrade

Multi_json also upgraded.

activesupport/activesupport.gemspec

@@ -19,6 +19,6 @@ Gem::Specification.new do |s|
   s.rdoc_options.concat ['--encoding',  'UTF-8']
 
   s.add_dependency('i18n',       '~> 0.6')
-  s.add_dependency('multi_json', '~> 1.0')
+  s.add_dependency('multi_json', '~> 1.3.0')
   s.add_dependency('tzinfo',     '~> 0.3.31')
 end

activesupport/lib/active_support/json/decoding.rb

@@ -9,7 +9,7 @@ module ActiveSupport
   module JSON
     class << self
       def decode(json, options ={})
-        data = MultiJson.decode(json, options)
+        data = MultiJson.load(json, options)
         if ActiveSupport.parse_json_times
           convert_dates_from(data)
         else
@@ -18,12 +18,12 @@ module ActiveSupport
       end
 
       def engine
-        MultiJson.engine
+        MultiJson.adapter
       end
       alias :backend :engine
 
       def engine=(name)
-        MultiJson.engine = name
+        MultiJson.use(name)
       end
       alias :backend= :engine=