Add kill() method to scheduler.
Write shutdown message to clients.

The server sends an array starting with the *shutdown* string followed
by the unix timestamp in milliseconds (Date.now()) plus the IP address
of the server.

This can be verified by connecting a client and executing the *monitor*
command and shutting down the server with a signal.

The monitor client will receive the message before the client connection
is closed by the server.

In process clients will also receive the message however it is not much
use to them as the process will exit shortly.
Load rdb file at start up.

Currently only handles string types, ignores expired keys and seems to
be substantially slower than redis with a tiny file which is to be
expected.
Add getset command handler.
0.1.50
Update docs, reinstate process exit on error.
0.1.51
Create hash on load.
Enable hash commands.