Fix prime and fibonacci numbers

[ChanhLeNguyen]

Fix prime and fibonacci numbers

[juhovan]

Feedback:

• It seems to work, good.
• Next time please don't use master, otherwise everything you push to master will get included in pull request
• Also please only do one feature change per branch and pull request to make it easier to review and make changes if there is something wrong
• Also try not to commit changes like removing tab on otherwise empty line, it only makes it harder to review as github will highlight the change
  • If you need to refactor old code do it in separate branch & pull request