Title 4: Code quality and open source

## Potential titles
- Writing code for others
## Table of contents (draft)
- Series introduction
- Code is for other people 
- Coding standards
  - Linting
- Testing
  - Unit tests
  - Functional tests
- Continuous Integration
- Contributing to open source
- Using an open source license
- Consuming open source code
- Conclusion, tips, & tools
