FIN packet added

A FIN packet was added that signals the end of the transaction. This will allow us to actually error on i/o timeouts instead of just assuming the transaction is over. If you update your master to v0.2 and don't upgrade your slaves then you will start seeing incorrect signature warnings. This is expected and v0.2 added a forward-compatible check to prevent this in the future. Upgrading your slaves first and then the master is the recommended upgrade strategy.

A version --version flag was also added for official releases. See readme for how to customize the version at compile time.