add sample benchmark config file

.gitignore

@@ -23,3 +23,5 @@ Gemfile.lock
 .*.swo
 .*.swm
 *.pid
+
+config/benchmark.yml

config/benchmark.yml

-seed_size:
-  commentables: 1
-  users: 1
-  threads: 5
-  top_comments: 0
-  sub_comments: 0
-  votes: 0
-  tags: 0

config/benchmark.yml.sample

+seed_size:
+  commentables: 20
+  users: 100
+  threads: 1000
+  top_comments: 1000
+  sub_comments: 2000
+  votes: 10000
+  tags: 100