estimatedDocumentCount to countDocuments (#252)

* Set default for counting of total documents to . Added option for using of  instead.

* Fixed typo

Author: giovannilobitos

lib/service.js

@@ -30,6 +30,7 @@ class Service {
     this.lean = options.lean === undefined ? true : options.lean;
     this.overwrite = options.overwrite !== false;
     this.events = options.events || [];
+    this.useEstimatedDocumentCount = !!options.useEstimatedDocumentCount;
   }
 
   extend (obj) {
@@ -98,7 +99,7 @@ class Service {
     }
 
     if (count) {
-      return model.where(query).estimatedDocumentCount().exec().then(executeQuery);
+      return model.where(query)[this.useEstimatedDocumentCount ? 'estimatedDocumentCount' : 'countDocuments']().exec().then(executeQuery);
     }
 
     return executeQuery();