docs(returnOriginal): clarify that returnOriginal doesn't set new…

…, and link to `findOneAndUpdate()` tutorial

lib/index.js

@@ -147,7 +147,7 @@ Mongoose.prototype.driver = require('./driver');
  *
  * Currently supported options are:
  * - 'debug': If `true`, prints the operations mongoose sends to MongoDB to the console. If a writable stream is passed, it will log to that stream, without colorization. If a callback function is passed, it will receive the collection name, the method name, then all arugments passed to the method. For example, if you wanted to replicate the default logging, you could output from the callback `Mongoose: ${collectionName}.${methodName}(${methodArgs.join(', ')})`.
- * - 'returnOriginal': If `false`, changes the default `new` option to `findOneAndUpdate()`, `findByIdAndUpdate` and `findOneAndReplace()` to true.
+ * - 'returnOriginal': If `false`, changes the default `returnOriginal` option to `findOneAndUpdate()`, `findByIdAndUpdate`, and `findOneAndReplace()` to false. This is equivalent to setting the `new` option to `true` for `findOneAndX()` calls by default. Read our [`findOneAndUpdate()` tutorial](/docs/tutorials/findoneandupdate.html) for more information.
  * - 'bufferCommands': enable/disable mongoose's buffering mechanism for all connections and models
  * - 'useCreateIndex': false by default. Set to `true` to make Mongoose's default index build use `createIndex()` instead of `ensureIndex()` to avoid deprecation warnings from the MongoDB driver.
  * - 'useFindAndModify': true by default. Set to `false` to make `findOneAndUpdate()` and `findOneAndRemove()` use native `findOneAndUpdate()` rather than `findAndModify()`.