Improvement: add yoda and no-cond-assign eslint rules

[robkebab]

Slightly improves readability in my opinion :) Feel free to reject if the community doesn't feel the same.

• Improve consistency of the code.
• Remove conditionals where the literal comes first (e.g. 'GET' !== method). Yoda rule reference for why this is generally suggested.
• Remove assignment in conditionals (goes hand-in-hand with no yoda). No-cond-assignment rule reference for why this is generally suggested.

[UlisesGascon]

Hi @robkebab!

I appreciate your efforts in improving the code readability – it's definitely a step in the right direction. 🥳

However, it appears that there are issues with the CI for Node.js 8 and 9. From my observation, it seems like there might be errors with the CI machine, as some tests are marked as 'pending' without providing a clear pass or fail status.

I am not able to re-run the CI due permissions, @dougwilson can you run them again? 🙏