small sentence fixes + added usage examples in belongsTo comments

lib/abstract-class.js

@@ -709,6 +709,23 @@ AbstractClass.hasMany = function hasMany(anotherClass, params) {
  *
  * @param {Class} anotherClass - class to belong
  * @param {Object} params - configuration {as: 'propertyName', foreignKey: 'keyName'}
+ *
+ * {Usage examples}
+ * Suppose model Post have a {belongsTo} relationship with User (the author of the post). You could declare it this way:
+ * Post.belongsTo(User, {as: 'author', foreignKey: 'userId'});
+ *
+ * When a post is loaded, you can load the related author with:
+ * post.author(function(err, user) {
+ *   // the user variable is your user object
+ * });
+ *
+ * The related object is cached, so if later you try to get again the author, no additional request will be made.
+ * But there is an optional boolean parameter in first position that set whether or not you want to reload the cache:
+ * post.author(true, function(err, user) {
+ *   // The user is reloaded, even if it was already cached.
+ * });
+ *
+ * This optional parameter default value is false, so the related object will be loaded from cache if available.
  */
 AbstractClass.belongsTo = function (anotherClass, params) {
     var methodName = params.as;
@@ -734,7 +751,7 @@ AbstractClass.belongsTo = function (anotherClass, params) {
             p = refresh;
             refresh = false;
         } else if (arguments.length > 2) {
-            throw new Error('Method only can\'t be only called with more than two arguments');
+            throw new Error('Method can\'t be called with more than two arguments');
         }
         var self = this;
         var cachedValue;
@@ -811,7 +828,7 @@ function defineScope(cls, targetClass, name, params, methods) {
                         saveOnCache = false;
                     }
                 } else {
-                    throw new Error('Method only can be only called with one or two arguments');
+                    throw new Error('Method can be only called with one or two arguments');
                 }
 
                 if (!this.__cachedRelations || (typeof this.__cachedRelations[name] == 'undefined') || actualRefresh) {