Enable binary file mode for external files

Author: dalizard

lib/rspec_api_documentation/writers/general_markup_writer.rb

@@ -12,7 +12,7 @@ def write
           markup_example = markup_example_class.new(example, configuration)
           FileUtils.mkdir_p(configuration.docs_dir.join(markup_example.dirname))
 
-          File.open(configuration.docs_dir.join(markup_example.dirname, markup_example.filename), "w+") do |f|
+          File.open(configuration.docs_dir.join(markup_example.dirname, markup_example.filename), "wb+") do |f|
             f.write markup_example.render
           end
         end