Qualify all item slugs to the mod which adds them #53

* Change default item URL to fall under /mod/<mod slug>/<item slug>
  but kept the old URL pattern around with the old behavior (i.e.,
  find the first item with that slug)
* Update Item to have a `qualifiedSlug` property which combines the
  item's own slug with its Mod's slug.  Updated a lot of code all
  over to use this in preference to the plain slug.
* Add a `localizeTo` method to Inventory to allow non-qualified slugs
  to be converted into qualified slugs within the inventory's stacks
* Update ModPack to work with either qualified or unqualified slugs
  for relevant methods
* Fix model state changes to happen before related events are
  triggered
* Add a debounce to the CraftingPlan object when triggering a recraft
  due to changes in related objects (esp. its inventories)
* Update the Inventory's sort to keep items sorted by mod before name
  with the Minecraft items sorted to the top
* Fix `ModPack.findItemByName` to actually recursively use the Mod's
  method instead of slugifying the given name and looking for the
  slug (since this won't necessarily work anymore).
* Ensure each Mod is assigned a reference to its containing ModPack
* Fix NameFinder to only consider an item non-gatherable if it is
  also craftable
* Update ModVersionParserV1 to assign qualified slugs to recipes
  for any items which are in the same mod (leaving any other slugs
  unqualified)
* Add Underscore mixins for composing and decomposing slugs
* Update old tests for the use of qualified slugs, and some new tests
  for the new methods added

test/mod_version.test.coffee

@@ -91,5 +91,5 @@ describe 'mod_version.coffee', ->
             """
 
         it 'finds all recipes which list item as output', ->
-            recipes = modVersion.findRecipes 'bucket'
-            (r.output[0].slug for r in recipes).sort().should.eql ['bucket', 'cake', 'cake']
+            recipes = modVersion.findRecipes 'test__bucket'
+            (r.output[0].slug for r in recipes).sort().should.eql ['test__bucket', 'test__cake', 'test__cake']