+ Added ServerMap::empty()
 + Added signature for VsfsRpcClient::mkdir()
 + Added RpcClientFactory
 + Added TestRpcClientFactory for test purpose
 * Move TestMockRpcClientFactory to rpc/mock_rpc_clients.h
 * Fixed the compiling issues for TestRpcClientFactory
 + Added a simple test case for VsfsRpcClient::mkdir()
 * Better comments on RpcClientFactory
 + Added back mkdir() to the VsfsClient interface class
 * Fixed virtual abstract function mkdir()
Merge pull request #44 from vsfs/client_mkdir

Add VsfsRpcClient::mkdir() and tons of test infrastructure.