v0.2.0

• Optimize Client::getSpaceIdByName()
• Replace SocketConnection with StreamConnection
• Move classes under the Tarantool\Client namespace
• Move the Request::TYPE_ERROR constant to Response
• Require a packer object to be passed explicitly to the Client constructor
• Validate IPROTO greeting messages
• Allow to pass custom MessagePack's packer and unpacker objects to the PurePacker constructor
• Add composite keys support for update requests, allow to pass a scalar key to DeleteRequest/SelectRequest constructors
• Add more tests