Update README.md and Demo.ipynb to include non-SSL connection option

This change request introduces an optional configuration for users who are working in a development environment and do not have SSL certificates. The proposed updates provide instructions on how to disable the secured connection by setting the 'insecure' parameter to True. This update is reflected in both the README.md file and the Demo.ipynb Jupyter notebook.

It's critical to emphasize that this configuration is strictly for development purposes and should not be used in a production environment.

Please find the proposed changes below:

Change 1: In the README.md, the following lines have been added to provide guidance for users without SSL certificates:

Or, if you do not have SSL certificates you may choose to switch off secured connection (do not do this in a production environment!):

fluent = Fluent("127.0.0.1", 50052, insecure=True)

Change 2: In the Demo.ipynb Jupyter notebook, the following comment has been updated to inform users about turning off SSL during development:

Finally, if you need SSL certificates to run this line. If you do a development work, you may turn SSL off with the parameter "insecure=True'.

f = Fluent('127.0.0.1', 50052, insecure=True)  # Only for development environment!