Initial client impl.

Initial work on the client.

A `GenServer` starts and is linked to a Java server, if the JVM process dies it is automatically restarted. The Java server manages a HBase client that requests are dispatched to which makes queries to HBase.

In this initial release only the [`HBaseClient#stats()`](http://tsunanet.net/~tsuna/asynchbase/api/org/hbase/async/HBaseClient.html#stats()) method has been implemented (demonstrated below). There's also no client API yet, `GenServer` calls must be made directly.

Part of the future work includes a proper module for the client interface.

```elixir
$ iex --name "diver@127.0.0.1" --cookie "mycookie" -S mix
iex(diver@127.0.0.1)1> proc = {:diver_java_server, :"__diver__diver@127.0.0.1"}
{:diver_java_server, :"__diver__diver@127.0.0.1"}
iex(diver@127.0.0.1)2> GenServer.call(proc, {:stats})
{:client_stats,
 [connections_created: 0, root_lookups: 0, scanners_opened: 0, gets: 0,
  num_rpc_delayed_due_to_nsre: 0, no_such_region_exceptions: 0, row_locks: 0,
  contended_meta_lookups: 0, scans: 0, puts: 0, num_batched_rpc_sent: 0,
  flushes: 0, atomic_increments: 0, uncontended_meta_lookups: 0, deletes: 0]}
```