message: Add 0.7.x section and "Color Columns" game
diff: This is a place for people to pimp their stuff that is built with ggez. If you want your project listed here, add it and
  submit a PR, please!
  +# 0.7.x
  +
  +## Games!
  +
  +* <https://github.com/rdrmic/color-columns>: A falling-blocks-type 2D game with a simple but addictive gameplay
  +
  +## Example/tutorial code
  +
  +None yet!
  +
  # 0.6.x
  ## Games!
  