Refactor all the examples for consistency and simplicity

[kabirbaidhya]

Refactor examples for consistency and simplicity.

• Refactor node example
• Refactor express example
• Refactor logger - add timestamp and tweaked the format a bit

New output for both examples

2019-09-28T11:08:35.261Z [ INFO ] HTTP server listening on port 3000!
2019-09-28T11:08:39.987Z [ DEBUG ] f1aa3c12 - Persisted a: 20
2019-09-28T11:08:39.987Z [ DEBUG ] f1aa3c12 - Persisted b: 30
2019-09-28T11:08:39.988Z [ DEBUG ] f1aa3c12 - Simulating delayed access
2019-09-28T11:08:39.988Z [ DEBUG ] f1aa3c12 - Calculated sum: 50
2019-09-28T11:08:39.988Z [ DEBUG ] f1aa3c12 - Persisted sum: 50
2019-09-28T11:08:39.991Z [ INFO ] f1aa3c12 - Response sent
2019-09-28T11:08:40.003Z [ DEBUG ] 81992355 - Persisted a: 10
2019-09-28T11:08:40.003Z [ DEBUG ] 81992355 - Persisted b: 50
2019-09-28T11:08:40.003Z [ DEBUG ] 81992355 - Simulating delayed access
2019-09-28T11:08:40.003Z [ DEBUG ] 81992355 - Calculated sum: 60
2019-09-28T11:08:40.003Z [ DEBUG ] 81992355 - Persisted sum: 60
2019-09-28T11:08:40.003Z [ INFO ] 81992355 - Response sent
2019-09-28T11:08:40.014Z [ DEBUG ] 66fe2219 - Persisted a: 50
2019-09-28T11:08:40.014Z [ DEBUG ] 66fe2219 - Persisted b: 100
2019-09-28T11:08:40.014Z [ DEBUG ] 66fe2219 - Simulating delayed access
2019-09-28T11:08:40.015Z [ DEBUG ] 66fe2219 - Calculated sum: 150
2019-09-28T11:08:40.015Z [ DEBUG ] 66fe2219 - Persisted sum: 150
2019-09-28T11:08:40.015Z [ INFO ] 66fe2219 - Response sent
2019-09-28T11:08:41.988Z [ INFO ] f1aa3c12 - Store contents: {"a":"20","b":"30","sum":50}
2019-09-28T11:08:42.003Z [ INFO ] 81992355 - Store contents: {"a":"10","b":"50","sum":60}
2019-09-28T11:08:42.015Z [ INFO ] 66fe2219 - Store contents: {"a":"50","b":"100","sum":150}