Add option to add hyperlink to image via insert_image

Added two more params to insert_image: 
```      
        Insert an image with its top-left corner in a worksheet cell.
        Args:
            row:     The cell row (zero indexed).
            col:     The cell column (zero indexed).
            image:   Path and filename for image in PNG, JPG or BMP format.
            options: Position and scale of the image.
            url:     Hyperlink url.
            tip:     An optional tooltip.
```

I also added testcases, let me know what you think.