Implemented modifier

lib/model.js

@@ -9,6 +9,7 @@ var dateToJSON = function () { return { $$date: this.getTime() }; }
   , util = require('util')
   , _ = require('underscore')
   , modifierFunctions = {}
+  , lastStepModifierFunctions = {}
   , comparisonFunctions = {}
   , logicalOperators = {}
   ;
@@ -213,6 +214,22 @@ function compareThings (a, b) {
 // Updating documents
 // ==============================================================
 
+
+lastStepModifierFunctions.$set = function (obj, field, value) {
+  obj[field] = value;
+};
+
+function findLastModificationStep (modifier, obj, field, value) {
+  var fieldParts = typeof field === 'string' ? field.split('.') : field;
+
+  if (fieldParts.length === 1) {
+    lastStepModifierFunctions[modifier](obj, field, value);
+  } else {
+    obj[fieldParts[0]] = obj[fieldParts[0]] || {};
+    modifierFunctions[modifier](obj[fieldParts[0]], fieldParts.slice(1), value);
+  }
+}
+
 /**
  * Set field to value in a model
  * Create it if it doesn't exist