Make parallel the default

lib/haml_lint/options.rb

@@ -10,7 +10,7 @@ class Options
     # @param args [Array<String>] arguments passed via the command line
     # @return [Hash] parsed options
     def parse(args)
-      @options = {}
+      @options = default_options
 
       OptionParser.new do |parser|
         parser.banner = "Usage: #{APP_NAME} [options] [file1, file2, ...]"
@@ -32,6 +32,10 @@ def parse(args)
 
     private
 
+    def default_options
+      { parallel: true }
+    end
+
     def add_linter_options(parser) # rubocop:disable Metrics/AbcSize, Metrics/MethodLength
       parser.on('--auto-gen-config', 'Generate a configuration file acting as a TODO list') do
         @options[:auto_gen_config] = true

spec/haml_lint/options_spec.rb

@@ -7,6 +7,12 @@
     subject { super().parse(args) }
     let(:args) { [] }
 
+    context 'without options' do
+      it 'sets the default values' do
+        subject[:parallel].should == true
+      end
+    end
+
     context 'with a configuration file specified' do
       let(:args) { %w[--config some-config.yml] }