Merge branch 'add-frozen-string-literal-to-community-contribution-files' into 'master'

Add frozen_string_literal to recently-added files from the community

See merge request gitlab-org/gitlab-ce!21132

lib/banzai/filter/project_reference_filter.rb

+# frozen_string_literal: true
+
 module Banzai
   module Filter
     # HTML filter that replaces project references with links.

lib/banzai/reference_parser/project_parser.rb

+# frozen_string_literal: true
+
 module Banzai
   module ReferenceParser
     class ProjectParser < BaseParser

spec/lib/banzai/filter/project_reference_filter_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe Banzai::Filter::ProjectReferenceFilter do

spec/lib/banzai/reference_parser/project_parser_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe Banzai::ReferenceParser::ProjectParser do