AI movement for mobs: - Githubissues

[x] mob should move back and forth until player is in range
- need an inRange function for each mob, probably a method of monster class that takes a range parameter from the child
[x] define "range" for mob detection
- [x] scale to size of tile
- [x] some mobs will have greater range than others:
  - cyclops should be short
  - wyvern should be VERY long
  - goblin should be mid range
  - wraith should be tile dimension because it's always edging closer
- [x] this should be an intrinsic property of each mob's class
[x] when player is in range, mob starts moving towards the player (if able)
- we can later enhance the AI to go around obstacles
- [x] store char it's walking over, replace once its gone
- [x] if obstructed, just keeps trying until it isn't
- [x] AI should seek to decrease difference in distance between itself and player in whichever dimension (x, y) has a greater difference

K-Mistele / seeker-of-the-sword