Rust Quest 0.2.0

Run git pull and cargo run to update.

• Fixed quests that used stuff from later lessons. The lesson 1 boss
  needed if and loops, which only come in lesson 2. Went through all
  30 lessons and fixed the rest.
• Quests you haven't opened yet now update when you pull. Ones you
  already worked on are left alone. If there's a newer version, the
  quest tells you and restore gets it. Your old file goes to
  .quest/backup/.