fixed normal map generation
added an item and inventory system

- an item class has been added that functions much like the Entity class in that:
   * it extends the Glyph class so that items may have an appearance
   * is defined by a template which lists an items properties
- item templates are defined in items. js
   * each item must have a use() function, which defines its behavior. The function takes a user and target parameter
   * I resisted the tempation to use mixins for items with similar effects (healing items, damage items, etc),
     as it seemed like over-engineering at this stage.
- items are managed by an inventory class, which keeps track of items and quantities
   * items are added using addItem(), where items are given a letter (for using) and pushed into the array
   * because of the way that Inventory was designed, even monster inventories will be given letters, though
     they won't be used
added an item and inventory system

- an item class has been added that functions much like the Entity class in that:
   * it extends the Glyph class so that items may have an appearance
   * is defined by a template which lists an items properties
- item templates are defined in items. js
   * each item must have a use() function, which defines its behavior. The function takes a user and target parameter
   * I resisted the tempation to use mixins for items with similar effects (healing items, damage items, etc),
     as it seemed like over-engineering at this stage.
- items are managed by an inventory class, which keeps track of items and quantities
   * items are added using addItem(), where items are given a letter (for using) and pushed into the array
   * because of the way that Inventory was designed, even monster inventories will be given letters, though
     they won't be used
Merge branch 'items' of ssh://github.com/a-out/avast_roguelike into items
moved Player and Maps storage into Dungeon class

- Dungeon is a global repository for storing the state of the dungeon as it is
  generated
- its also used to make the player a global reference
- stores a reference to the current map, as well as every generated map thus far
added inventory mixin for Player entity

- this should probably be refactored later on
  * Items share too many aspects in common with Entities for them not to be
    related somehow
  * The use() aspect of an item can be converted into a mixin of some sort
  * Though it seems unintutive, the Game.Mixins.Item could be abstracted into
    the class through isItem() and use() methods
refactored an Actor class

- Actor is made out of the differences between Entity and Item

		Glyph
		  |
		Entity
		/   \
 	     Item   Actor

- Actor contains the mixin system, as well as combat stats
created a messaging queue
created getItemsAt() to get multiple items
added pickUp to PlayerInventory mixin
added quaff mixin
added method to list items for some action
added universal use() method and getAllType()
added acid potion
added item selection capability
more item management methods
items now have uses
added some comments
new helper methods for specific maps
added upstairs and downstairs tiles