Fixes bug when creating Models without all data (#69)

Getters/setters for properties would not be correctly defined

Author: dresende

lib/Instance.js

@@ -236,6 +236,12 @@ function Instance(opts) {
 		addInstanceProperty(opts.id);
 	}
 
+	for (var k in opts.properties) {
+		if (opts.properties.hasOwnProperty(k) && !opts.data.hasOwnProperty(k) && k != opts.id) {
+			opts.data[k] = null;
+		}
+	}
+
 	for (var k in opts.data) {
 		if (!opts.data.hasOwnProperty(k)) continue;
 		if (!opts.properties.hasOwnProperty(k) && k != opts.id && opts.association_properties.indexOf(k) == -1) {