fix b0rken test, i owe you ice cream

spec/lib/guard/rails/runner_spec.rb

@@ -17,6 +17,7 @@ describe Guard::RailsRunner do
       let(:pid) { 12345 }
 
       before do
+        FileUtils.mkdir_p File.split(runner.pid_file).first
         File.open(runner.pid_file, 'w') { |fh| fh.print pid }
       end