Session05 - Final mailroom.py and safe_input.py

Final Mailroom madness and Exceptions assignments
I'm not convinced there's a benefit to instantiating an `OrderedDict` here. Lines 122-132 iterate over the contents of the dictionary, but the same could be done with the list bound to `sort`. I'm not saying it's wrong--An argument could be made that by using a dictionary you make the code more readable by allowing value lookup by key rather than index--but that your code doesn't take advantage of most of the properties of a dictionary, so creating one seems like an unnecessary step.