Update vendor/underscore and backbone.

Former-commit-id: 614926653b0b1669f8a5533666adb0aecbd46c03

vendor/underscore/underscore.js

@@ -267,7 +267,7 @@
 
   // Sort the object's values by a criterion produced by an iterator.
   _.sortBy = function(obj, val, context) {
-    var iterator = _.isFunction(val) ? val : function(obj) { return obj[val]; };
+    var iterator = lookupIterator(obj, val);
     return _.pluck(_.map(obj, function(value, index, list) {
       return {
         value : value,
@@ -281,16 +281,38 @@
     }), 'value');
   };
 
+  // An internal function to generate lookup iterators.
+  var lookupIterator = function(obj, val) {
+    return _.isFunction(val) ? val : function(obj) { return obj[val]; };
+  };
+
+  // An internal function used for aggregate "group by" operations.
+  var group = function(obj, val, behavior) {
+    var result = {};
+    var iterator = lookupIterator(obj, val);
+    each(obj, function(value, index) {
+      var key = iterator(value, index);
+      behavior(result, key, value);
+    });
+    return result;
+  };
+
   // Groups the object's values by a criterion. Pass either a string attribute
   // to group by, or a function that returns the criterion.
   _.groupBy = function(obj, val) {
-    var result = {};
-    var iterator = _.isFunction(val) ? val : function(obj) { return obj[val]; };
-    each(obj, function(value, index) {
-      var key = iterator(value, index);
+    return group(obj, val, function(result, key, value) {
       (result[key] || (result[key] = [])).push(value);
     });
-    return result;
+  };
+
+  // Counts instances of an object that group by a certain criterion. Pass
+  // either a string attribute to count by, or a function that returns the
+  // criterion.
+  _.countBy = function(obj, val) {
+    return group(obj, val, function(result, key, value) {
+      result[key] || (result[key] = 0);
+      result[key]++;
+    });
   };
 
   // Use a comparator function to figure out the smallest index at which
@@ -709,7 +731,7 @@
   };
 
   // Internal recursive comparison function for `isEqual`.
-  function eq(a, b, stack) {
+  var eq = function(a, b, stack) {
     // Identical objects are equal. `0 === -0`, but they aren't identical.
     // See the Harmony `egal` proposal: http://wiki.ecmascript.org/doku.php?id=harmony:egal.
     if (a === b) return a !== 0 || 1 / a == 1 / b;
@@ -794,7 +816,7 @@
     // Remove the first object from the stack of traversed objects.
     stack.pop();
     return result;
-  }
+  };
 
   // Perform a deep comparison to check if two objects are equal.
   _.isEqual = function(a, b) {
@@ -832,7 +854,7 @@
       return toString.call(obj) == '[object ' + name + ']';
     };
   });
-  
+
   // Define a fallback version of the method in browsers (ahem, IE), where
   // there isn't any inspectable "Arguments" type.
   if (!_.isArguments(arguments)) {