Add shebang to list_lab. Submit dict/set lab, mailroom, safe_input

All of the assignments being submitted here are complete. Are we supposed to make a pull request with a different branch anyway?
You could also eliminate the userin variable and just ```return raw_input(...)``` on line 5. The try-catch mechanics will hang on to the return value for you and do the right thing. In the case of an exception, the return value will be overwritten by the value in the except block.