Kristin_Mod0_Week6_IC

[KMPWeiland]

This PR addresses initial bugs in and adds functionality to the Shiny-Giggle Project. Key elements include:

• Debugs initial setup to get tests to pass based on the provided pry interaction pattern.
• Adds add_bid and current_high_bid methods to handle bid placement and track the highest bid on an item (and corresponding tests).
• Adds unpopular_items method to list items without bids
• Adds potential_revenues method to calculate sum of highest bids per item
• Adds auction_bidders to list unique bidders
• Adds bidder_info method to return details about bidders budgets and the items on which they bid
• Plus corresponding tests to the above