Naming, namedtuples, ValidCardCheck bug

+ Fixed a bug in trick.ValidCardCheck that let a player enter a
negative number
  when prompted to play a card
+ Updated naming to comply with style guide (camel case, constants)
+ Switch ranks from dictionary to namedtuple. This makes the printing
methods a
  lot easier to read and write and doesn't require me to pass the deck
to those
  methods
+ Sanitize variable names so that type is not in them