v2.3.0

This release, along with several bugfixes, contains new functionality:

• Client.Truncate (#73, 2f11406) (thanks @junjieqian!)
• Client.ServerDefaults (039ab59)

It contains one potentially dangerous behaviour change, in b02ab58: FileWriter.Close now will correctly propagate errors in the situation where the namenode has not yet received all acks from the datanodes. Close returns a specific error in that case, ErrReplicating, which the client can either ignore or use in a retry loop. See also IsErrReplicating, for checking this case.