Added more examples to comparison_with_sql documentation
- [ ] closes #xxxx
- [ ] tests added / passed
- [x ] passes `git diff upstream/master | flake8 --diff`
- [x ] whatsnew entry
  added the following examples:
  - Top N rows with offset 
  - Top N rows per group
  - ROW_NUMBER() OVER(PARTITION BY day ORDER BY total_bill DESC)
  - UPDATE
  - DELETE
