Added support for setting the debugger (-u flag)

lib/guard/rails.rb

@@ -13,7 +13,8 @@ module Guard
         :start_on_start => true,
         :force_run => false,
         :timeout => 20,
-        :server => nil
+        :server => nil,
+        :debugger => nil
       }
 
     def initialize(watchers = [], options = {})

lib/guard/rails/runner.rb

@@ -33,6 +33,7 @@ module Guard
       rails_options = [
         '-e', options[:environment],
         '-p', options[:port],
+        '-u', options[:debugger],
         '--pid', pid_file
       ]
 

spec/lib/guard/rails/runner_spec.rb

@@ -46,6 +46,14 @@ describe Guard::RailsRunner do
         runner.build_rails_command.should match(%r{ -d})
       end
     end
+    
+    context 'debugger' do
+      let(:options) { default_options.merge(:debugger => true) }
+
+      it "should have a debugger switch" do
+        runner.build_rails_command.should match(%r{ -u})
+      end
+    end
 
     context 'custom server' do
       let(:options) { default_options.merge(:server => 'thin') }