increase number of gems for contributors -- fixes https://github.com/HabitRPG/habitrpg/issues/3933

Replaces old PR https://github.com/HabitRPG/habitrpg/pull/3956

@lefnire: Edit `20140831_increase_gems_for_previous_contributions.js` to uncomment one of the "var dbUsers" lines, then run it, capturing STDOUT to a file. Save the file somewhere safe so that if any contributors tell us that they haven't received their correct gem increase, we can check what actually happened.

- Finds all contributors (tier 8 and below) and increases their gems.
- Displays output for every user to show how many gems they had and how many are added.
- Does a separate db query after that to retrieve and display the new balances.

It might be a little bit over-engineered now... I started programming and forgot to stop. But good record-keeping is important for gem increases. :)

Note @lemoness's [comment in the original PR](https://github.com/HabitRPG/habitrpg/pull/3956#issuecomment-53974172): _"@lefnire text me when you run these; will send you text for a Bailey announcement/handle SM announcement"_