get api no metadata

First, thank you for your work on this etcd client.

The `get` method returns only the key-value pair (`kv`), without any metadata.
So I can't retrieve the leaseID associated with a key.

by the way, there are some Inaccuracies in readme
- The package name for installation appears to be incorrect, should be `pip install etcd-client-py`
- The import statement should be `from etcd_client import Client `

Let me know if you need any clarification or additional information about these problems.