Rename messages
Merge pull request #118 from edrevo/rename-messages

Rename messages
Remove preStart form SellerExchangeActor
Merge pull request #119 from edrevo/remove-prestart

Remove preStart form SellerExchangeActor
Modify exchange algorithm to avoid sending offers
Merge pull request #121 from edrevo/avoid-offers

Modify exchange algorithm to avoid sending offers