Software engineering practices

[tianyin]

@Spedoske @tylergu Given that we are planning to open the project soon (e.g., for AE) and later even turn the project into an open-source endeavor, I think it's time to enforce some good software engineering efforts.

I love the PR practice @Spedoske started -- basically we should not directly push to the master branch, but trying to open PRs and merging PRs. It also enforces the regression tests to be run.

Moreover, I think we really should start to submit small, incremental PRs instead of gigantic PRs which is hard to review and merge. Please try to break your big PR into a number of small PRs and submit them.

Third, when merging PRs, please choose to "Squash the commits into one commit" -- basically each PR should be merged with only 1 commit, instead of multiple ones. This could make the commit history much cleaner and easy to maintain.

Lastly, let's follow the Action Plan practice and write and comment on action plan in time.