remove float from memory one

while working on the memory two strategies we observed that
when creating the transition rates dict of the strategy
there as a float argument. This argument seems to have been left
there by previous versions.

Author: Nikoleta Glynatsi

axelrod/strategies/memoryone.py

@@ -82,8 +82,7 @@ def set_four_vector(self, four_vector: Tuple[float, float, float, float]):
             raise ValueError("An element in the probability vector, {}, is not "
                              "between 0 and 1.".format(str(four_vector)))
 
-        self._four_vector = dict(zip([(C, C), (C, D), (D, C), (D, D)],
-                                     map(float, four_vector)))
+        self._four_vector = dict(zip([(C, C), (C, D), (D, C), (D, D)], four_vector))
         self.classifier['stochastic'] = any(0 < x < 1 for x in set(four_vector))
 
     def strategy(self, opponent: Player) -> Action: