title: Multiple consumers consuming from same topic
body: <p>I have 2 consumers say c1 belonging to group g1 and c2 belonging to group g2.
  I have a topic testing with 100 messages. 
  c1 has read the messages and auto commit is enabled.
  Now if i start c2 should it start consuming from offset 0 ? If so I am not able to consume the messages from start in a different group</p>