Following steps1

[mikefhsu]

1. Apply a standard Python template to the code
2. Use Python's argument parser to parse the user's inputs. The command we need is like
   python yourScript.py -i http://address -o /your/local/directory
3. The current filename after downloaded is not meaningful. Need to parse the original file name and use it rename the local file name
4. Create local directory if it does not exist
5. Error handling for erroneous input address
6. Test cases