Add newline to benchmark output.

Fix #47.
diff --git a/benchmark/output.html b/benchmark/output.html
index 71e5771..3330a63 100644
--- a/benchmark/output.html
+++ b/benchmark/output.html
@@ -364,4 +364,4 @@
 "pub serve" is compiling test/my_app_test.dart...
 "pub serve" is compiling test/utils_test.dart...
 00:00 +42: All tests passed!
-</code></pre>
\ No newline at end of file
+</code></pre>