Update SAYT algo to give better matches

The algorithm will now give higher rankings to items containing
multiple sequential letters which match, and higher rankings to
those whose length more closely matches the given term.

src/client/models/site/item_selector.coffee

@@ -47,25 +47,36 @@ module.exports = class ItemSelector extends BaseModel
 
     # Private Methods ##############################################################################
 
-    _isMatch: (name, itemSlug)->
+    _computeScore: (name, itemSlug)->
         hintIndex  = 0
         hintLetter = @_hint[hintIndex]
         name       = name.toLowerCase()
+        nextScore  = 1
+        totalScore = 0
 
         for nameIndex in [0...name.length] by 1
             if name.charAt(nameIndex) is hintLetter
+                totalScore += nextScore
+                nextScore += 1
                 hintIndex += 1
                 if hintIndex is @_hint.length
                     item = @_modPack.findItem itemSlug
-                    return false unless item?
-                    return @_isAcceptable item
-                hintLetter = @_hint[hintIndex]
+                    return 0 unless item?
+                    return 0 unless @_isAcceptable item
+                    break
 
-        return false
+                hintLetter = @_hint[hintIndex]
+            else
+                nextScore = 1
+
+        return 0 if hintIndex < @_hint.length
+
+        totalScore *= @_hint.length / name.length
+        return totalScore
 
     _refreshResults: ->
         oldResults = @_results
-        newResults = {}
+        scoredItems = []
         count = 0
 
         logger.verbose => "Looking for items which match: #{@_hint}"
@@ -75,15 +86,18 @@ module.exports = class ItemSelector extends BaseModel
                 return unless mod.enabled
 
                 mod.eachName (name, itemSlug)=>
-                    return if count >= @_maxResults
+                    return if scoredItems.length >= @_maxResults
+                    return unless itemSlug.isQualified
 
-                    if @_isMatch name, itemSlug
-                        if itemSlug.isQualified
-                            newResults[itemSlug] = itemSlug
-                            count += 1
+                    score = @_computeScore name, itemSlug
+                    if score >= @_hint.length
+                        scoredItems.push score:score, itemSlug:itemSlug
 
-        newResults = _.values(newResults)
-        newResults.sort ItemSlug.compare
+        scoredItems.sort (a, b)->
+            if a.score isnt b.score
+                return if a.score > b.score then -1 else +1
+            return ItemSlug.compare a.itemSlug, b.itemSlug
 
+        newResults = (e.itemSlug for e in scoredItems)
         @_results = newResults
         @trigger c.event.change + ':results', this, oldResults, newResults