Add shopping_list.py
Add method containg help messages.
Remove redundant semicolons.
Add an item to the shopping list.
Implement method to show contents of the list.
Implement main loop.

Take input from user and add it to the shopping list. Display help
messages and contents of the list. Terminate program when DONE is
inputted.
Fix indentation.

Tab spaces should be 4 spaces wide.
Show the final list once the user ends the program.
Merge pull request #1 from adityatrivedi/development

Implement basic shopping list program.