Example code for basic Call and Prepare/Flush.

Example functions for a simple Put & Get using Call(), and then for
Prepare() & Flush().

Each example is self-contained, and includes the server
setup/teardown.  This makes the code closer to what would be used in
an actual client program.

The Prepare() & Flush() is a bit long because we have to create the values
we are later scanning for.
this, again, should not be something you would have to check for in practice (unless I am wrong).
If a key doesn't exist, you should still get a Value, but with a nil Bytes slice.