Minor usage improvements

#### Allow creating passing tint color

    PHFRefreshControl *refreshControl = [[PHFRefreshControl alloc] initWithTintColor:tintColor];

#### Adds notification by block

    [refreshControl setRefreshBlock:^{
        //some code
    }];

#### Refresh control creating directly from UIScrollView (category)

    [scrollView setRefreshControlWithTarget:dataController action:@selector(reload)]

or

    [scrollView setRefreshControlWithRefreshBlock:^{
        //some code
    }];