Remove defaults for ReadConsistency and WriteConsistency

* Removed constructors/apply with default value (ReadOne/WriteOne) for consistency in
  Get, Update and Delete messages
* The reason is that there is no good default. It depends, and is something that should
  be thought of by the user.
* WriteOne renamed to WriteLocal
* ReadOne renamed to ReadLocal
* WriteTwo and WriteThree removed, in favor of WriteTo(n)
* ReadTwo and ReadThree removed, in favor of ReadFrom(n)
* timeout parameter moved to ReadConsistency and WriteConsistency class.
  It is not appropriate for WriteLocal/ReadLocal.
  This also simplified the API.

Fixes #47