Refactor the serving client and server module

[leonwanghui]

What type of PR is this?

/kind enhancement

What does this PR do / why do we need it:

Currently the serving module (both client and server) is still in early stage, and causing some common problems (such as Issue #62). This PR is proposed to refactor the serving framework to make it easier to specify the dynamic ip address and port, and more importantly provide a more clear framework for developers to learn and enhance it.

The change of this PR contains:

• Design a unified entrance interface for both client and server module with Client and Server class
• Now the system can automatically detect if the server started or shutdown even without manually specified
• Users can specify the host ip and port when initializing Server and Client class
• Update the Flask listen path from http://127.0.0.1:5000/predict to http://127.0.0.1:5000/servables/<name> for predict request

How to use:

Before	After
from tinyms.serving import start_server, server_started, list_servables, predict, shutdown start_server() if server_started(): list_servables() predict('example.jpg', 'servable_name', dataset_name='mnist') shutdown()	from tinyms.serving import Client, Server server = Server() server.start_server() client = Client() client.list_servables() client.predict('example.jpg', 'servable_name', dataset_name='mnist') server.shutdown()

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewers: