Refactor 37 lines occurring 3 times in 3 files: Creeper.js, IronGolem.js, Zombie.js

[joshlory]

I've selected for refactoring 37 lines of code which are duplicated in 3 file(s) (1, 2, 3). Addressing this will make our codebase more maintainable and improve Better Code Hub's Write Code Once guideline rating! 👍

Here's the gist of this guideline:

• Definition 📖
  Do not copy code.
• Why❓
  When code is copied, bugs need to be fixed in multiple places. This is both inefficient and a source of regression bugs.
• How 🔧
  Avoid duplication by never copy/pasting blocks of code and reduce duplication by extracting shared code, either to a new unit or introduce a superclass if the language permits.

You can find more info about this guideline in Building Maintainable Software. 📖

[joshlory]

Same issue created via https://bettercodehub.com/results/code-dot-org/craft