fix: store('scope').update() ignores scope

Ensures that when calling `store('scope').update(...)`, that only items in scope are updated.  Items out of scope are ignored.

This code assumes the following:
* `storedObjects` is an array with the exact same size as `objectsOrIds`
* `objectsOrIds` is either a string, an object, a list of strings, or a list of objects
* if `objectsOrIds` is not an array then it is a single string representing an id or a single object and, as a result, `storedObjects` will either be null or a single object
* when attempting to find a single objectOrId, a single object is returned (rather than an array with one object)
* every item returned by find() will have an id associated with it.

lib/scoped/update.js

@@ -1,11 +1,59 @@
 module.exports = update
 
 var find = require('./find')
+var merge = require('lodash/merge')
 
 function update (type, api, objectsOrIds, change) {
   return find(type, api, objectsOrIds)
 
   .then(function (storedObjects) {
-    return api.update(objectsOrIds, change)
+    // objectsOrIds may contain updated information for the respective storedObject
+    // (e.g. _deleted = true), so incorporate all information in the objectOrId into
+    // the storedObject
+    var updatedObjects = updateObjectsAndFilterErrors(objectsOrIds, storedObjects)
+
+    return api.update(updatedObjects, change)
+
+    .then(function (apiUpdates) {
+      if (!Array.isArray(apiUpdates)) {
+        return apiUpdates
+      }
+
+      return restoreOriginalFindErrors(storedObjects, apiUpdates)
+    })
+  })
+}
+
+function updateObjectsAndFilterErrors (objectsOrIds, storedObjects) {
+  if (!Array.isArray(objectsOrIds)) {
+    return updateObject(objectsOrIds, storedObjects)
+  }
+
+  return storedObjects.map(function (storedObject, index) {
+    if (storedObject instanceof Error) {
+      return storedObject
+    }
+
+    return updateObject(objectsOrIds[index], storedObject)
+  }).filter(function (storedObject) {
+    return !(storedObject instanceof Error)
+  })
+}
+
+function updateObject (objectOrId, storedObject) {
+  if (typeof objectOrId !== 'object') {
+    return storedObject
+  }
+
+  return merge(storedObject, objectOrId)
+}
+
+function restoreOriginalFindErrors (foundObjects, apiUpdates) {
+  return foundObjects.map(function (foundObject) {
+    if (foundObject instanceof Error) {
+      return foundObject
+    }
+
+    return apiUpdates.shift()
   })
 }