Update README.md according to feedback
Update README.md according to feedback

- use shell prompt everywhere to be consistent
- reorder elasticsearch related topics
- add env variable info
- correct typo

1000miles/speakerinnen_liste,rubymonsters/speakerinnen_liste,1000miles/speakerinnen_liste,rubymonsters/speakerinnen_liste,1000miles/speakerinnen_liste,rubymonsters/speakerinnen_liste