Add testcase
Change code convention to follow PSR

Follow PSR mostly, except the below 2:

- This class can't have a namespace, because class declared in PHP extension
is global
- Method name need to be camelCase, will fix later
Rename method Connect() to connect()
Rename method Key() to getKey()
Rename method SocketRead() to readSocket(), SocketWrite() to writeSocket()
Rename property $aOption to $option
Rename property $iResultCode to $resultCode, $sResultMessage to $resultMessage
Rename property $aServer to $server
Rename property $rSocket to $socket
Write serialized data to socket

This will allow set/get method to work correctly with data type same as
original Memcached extension, including array and object, fixed #1