Injectable Locking interface

[Lewiscowles1986]

Issues such as #16 seem to stem from the inability to inject locking behaviour.

Right now to change the API would seem to break downstream clients, so I propose that a an optional parameter be added to the constructor for the stream wrapper for a locking interface, which would allow those who want network locking and alternative behaviours to create their own implementations and absolve the library of solving locking and stream wrapper bindings.