Remove redundant json dependency

MultiJson doesn't complain anymore

Author: rwz

Gemfile

@@ -3,6 +3,5 @@ source 'https://rubygems.org'
 gemspec
 
 gem 'rake'
-gem 'json', '~> 1.8'
 gem 'mocha', :require => false
 gem 'actionpack', '~> 3.0'

Gemfile.edge

@@ -3,7 +3,6 @@ source 'https://rubygems.org'
 gemspec
 
 gem 'rake'
-gem 'json', '~> 1.8'
 gem 'mocha', require: false
 
 git 'git://github.com/rails/rails.git', branch: '4-0-stable' do