Update project doctring and Readme with preview disclaimer

Author: samwelkanda

README.md

@@ -1,9 +1,11 @@
 [![CI Actions Status](https://github.com/microsoftgraph/msgraph-sdk-python-core/workflows/msgraph-sdk-python-core/badge.svg)](https://github.com/microsoftgraph/msgraph-sdk-python-core/actions)
 
-## Microsoft Graph Core Python Client Library
+## Microsoft Graph Core Python Client Library(Preview Version)
 
 The Microsoft Graph Core Python client library is a lightweight wrapper around the Microsoft Graph API. It provides functionality to create clients with desired configuration and middleware.
 
+**Disclaimer**: Please, be aware that preview versions of `msgraph-core` package are for testing purpose only. Do not use them in a production environment.
+
 ## Prerequisites
 
     Python 3.5+ (this library doesn't support older versions of Python)
@@ -20,8 +22,10 @@ To call Microsoft Graph, your app must acquire an access token from the Microsof
 
 ### 2. Install the required packages
 
-    `pip install msgraph-core`
-    `pip install azure-identity`
+Msgraph-core is available on PyPI
+
+    `python -m pip install msgraph-core`
+    `python -m pip install azure-identity`
 
 ### 3. Import modules
 

msgraph/__init__.py

@@ -3,8 +3,7 @@
 # Licensed under the MIT License.
 # -----------------------------------
 """
-Core component of the Microsoft Graph Python SDK consisting of HTTP/Graph Client and a configurable
-middleware pipeline
+Microsoft Graph Core Library for Python
 """
 from .core import SDK_VERSION