Fix frontmatter on 2.0

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

@@ -3,6 +3,7 @@ require 'json'
 require 'pathname'
 require 'middleman-core/util'
 require 'middleman-core/contracts'
+require 'backports/2.1.0/array/to_h'
 
 module Middleman::Util::Data
   include Contracts

middleman-core/middleman-core.gemspec

@@ -54,4 +54,5 @@ Gem::Specification.new do |s|
   # Hash stuff
   s.add_dependency('hashie', ['~> 3.4'])
   s.add_dependency('hamster', ['~> 1.0'])
+  s.add_dependency('backports', ['~> 3.6'])
 end