使用：
SGMAlbumViewController* viewVC = [[SGMAlbumViewController alloc] init];
viewVC.assetsLibrary =assetLibrary;
viewVC.limitNum = 3;//限制选择张数，不设置即不限制
[viewVC doSelectedBlock:^(NSMutableArray *assetDicArray) { //包含 {@"asset":ALAsset,@"assetIndex":0,@"select":@YES}
[selectedPhotoArray addObjectsFromArray:assetDicArray];
[mainTable reloadData];
}];
UINavigationController* nav = [[UINavigationController alloc]initWithRootViewController:viewVC];
[self presentViewController:nav animated:YES completion:nil];