Fixing the problem when RuboCop::Markdown.config_store was not filled.

This problem appeared when "rubocop-md" loaded via .rubocop.yml and used "--formater"

Fixes #22

lib/rubocop/markdown/rubocop_ext.rb

@@ -42,9 +42,10 @@ def markdown_file?(file)
 
 RuboCop::Runner.prepend(Module.new do
   # Set config store for Markdown
-  def initialize(*args)
-    super
+  def get_processed_source(*args)
     RuboCop::Markdown.config_store = @config_store
+
+    super
   end
 
   # Do not cache markdown files, 'cause cache doesn't know about processing.

test/fixtures/.rubocop.yml

@@ -0,0 +1,5 @@
+inherit_from:
+  - "../../.rubocop.yml"
+
+require:
+  - "rubocop-md"

test/fixtures/configs/no_autodetect.yml

@@ -1,4 +1,4 @@
-inherit_from: "../../../.rubocop.yml"
+inherit_from: "../.rubocop.yml"
 
 Markdown:
   Autodetect: false

test/fixtures/configs/no_warn_invalid.yml

@@ -1,4 +1,5 @@
-inherit_from: "../../../.rubocop.yml"
+inherit_from: "../.rubocop.yml"
 
 Markdown:
   WarnInvalid: false
+

test/integration_test.rb

@@ -6,11 +6,11 @@
 
 module RuboCopRunner
   def run_rubocop(path, options: "")
-    md_path = File.expand_path("../lib/rubocop-md.rb", __dir__)
     output, _status = Open3.capture2(
-      "bundle exec rubocop -r #{md_path} #{options} #{path}",
+      "bundle exec rubocop #{options} #{path}",
       chdir: File.join(__dir__, "fixtures")
     )
+
     output
   end
 end
@@ -26,6 +26,14 @@ def test_single_snippet_file
     assert_match %r{Style/StringLiterals}, res
   end
 
+  def test_file_with_format_options
+    res = run_rubocop("single_snippet.md", options: "--format progress")
+
+    assert_match %r{Inspecting 1 file}, res
+    assert_match %r{1 offense detected}, res
+    assert_match %r{Style/StringLiterals}, res
+  end
+
   def test_multiple_snippets_file
     res = run_rubocop("multiple_snippets.markdown")