Fixed issue in activity stream #3705

Refer Issue: #25

Review ID: 1983001
Merge pull request #26 from tarunbhardwaj/task-3705

Fixed issue in activity stream #3705
Merge branch 'hotfix/3.0.1.1' into develop
* Replacing all _json(self) to serialize(self, purpose=None) #3895
* Flake8ify
Review ID - 2733001
Fixed Flake8 issues #4202

Review ID: 2983001
Merge pull request #30 from aroraumang/feature/task-4202

Fixed Flake8 issues #4202
Merge pull request #29 from param107/feature/task-3895

Replacing all _json(self) to serialize(self, purpose=None) #3895
Release version 3.0.2.0
Merge branch 'release/3.0.2.0'