setup pre-commit hook + initial run against all files

[yunjunz]

Description of proposed changes

• install pre-commit GitHub Apps
• add .pre-commit-config.yaml
• changes from the initial run of pre-commit against all files
• info: printout h5 dataset compression info

Reminders

• Pass Codacy code review (green)
• Pass Circle CI test (green)
• If adding new functionality, add a detailed description to the documentation and/or an example.