Use native Ruby JSON implementation instead of ActiveSupport's.

middleman-core/lib/middleman-core/core_extensions/data.rb

@@ -9,7 +9,7 @@ module Middleman
         def registered(app)
           # Data formats
           require 'yaml'
-          require 'active_support/json'
+          require 'json'
 
           app.config.define_setting :data_dir, 'data', 'The directory data files are stored in'
           app.send :include, InstanceMethods
@@ -98,7 +98,7 @@ module Middleman
           if %w(.yaml .yml).include?(extension)
             data = YAML.load_file(full_path)
           elsif extension == '.json'
-            data = ActiveSupport::JSON.decode(full_path.read)
+            data = JSON.parse(full_path.read)
           else
             return
           end

middleman-core/lib/middleman-core/core_extensions/front_matter.rb

@@ -5,7 +5,7 @@ require 'pathname'
 require 'yaml'
 
 # Parsing JSON frontmatter
-require 'active_support/json'
+require 'json'
 
 # Extensions namespace
 module Middleman::CoreExtensions
@@ -154,7 +154,7 @@ module Middleman::CoreExtensions
 
         begin
           json = ($1 + $2).sub(';;;', '{').sub(';;;', '}')
-          data = ActiveSupport::JSON.decode(json).symbolize_keys
+          data = JSON.parse(json).symbolize_keys
         rescue => e
           app.logger.error "JSON Exception parsing #{full_path}: #{e.message}"
           return false