Add logging of all activities

[an-ju]

In order to build metrics and run analysis, we'd like to keep all activities that may happen in the system, such as

• voting (make a vote, reveal a vote, select a vote, and reset a vote)
• editing (edit a story's name or description)
• chatting (after we add chatting functionality to this app)
• navigating (order of viewing a page/project/story)

[an-ju]

Remaining behaviors to capture

• editing (in terms of keystroke history)
• chatting
• navigating across tabs (all stories vs. unestimated stories)