Multiple improvements and bug fixes (#66)

* Multiple improvements and bug fixes:

    * Using lazy stacking to save on memory when using a replay buffer
    * Remove step counting for evaluation episodes
    * Reset game between heatup and training
    * Major bug fixes in NEC (is reproducing the paper results for pong now)
    * Image input rescaling to 0-1 is now optional
    * Change the terminal title to be the experiment name
    * Observation cropping for atari is now optional
    * Added random number of noop actions for gym to match the dqn paper
    * Fixed a bug where the evaluation episodes won't start with the max possible ale lives
    * Added a script for plotting the results of an experiment over all the atari games

logger.py

@@ -115,6 +115,14 @@ class ScreenLogger(object):
                 if default is not None:
                     return default
 
+    def change_terminal_title(self, title: str):
+        """
+        Changes the title of the terminal window
+        :param title: The new title
+        :return: None
+        """
+        print("\x1b]2;{}\x07".format(title))
+
 
 class BaseLogger(object):
     def __init__(self):
@@ -157,6 +165,7 @@ class Logger(BaseLogger):
         self.time = None
         self.experiments_path = ""
         self.last_line_idx_written_to_csv = 0
+        self.experiment_name = ""
 
     def set_current_time(self, time):
         self.time = time
@@ -205,7 +214,9 @@ class Logger(BaseLogger):
 
     def signal_value_exists(self, time, signal_name):
         try:
-            self.get_signal_value(time, signal_name)
+            value = self.get_signal_value(time, signal_name)
+            if value != value:  # value is nan
+                return False
         except:
             return False
         return True
@@ -229,7 +240,8 @@ class Logger(BaseLogger):
         if self.start_time:
             self.create_signal_value('Wall-Clock Time', time.time() - self.start_time, time=episode)
         else:
-            self.create_signal_value('Wall-Clock Time', time.time(), time=episode)
+            self.create_signal_value('Wall-Clock Time', 0, time=episode)
+            self.start_time = time.time()
 
     def create_gif(self, images, fps=10, name="Gif"):
         output_file = '{}_{}.gif'.format(datetime.datetime.now().strftime('%Y-%m-%d-%H-%M-%S'), name)
@@ -243,7 +255,7 @@ class Logger(BaseLogger):
     def remove_experiment_dir(self):
         shutil.rmtree(self.experiments_path)
 
-    def print_summary(self):
+    def summarize_experiment(self):
         screen.separator()
         screen.log_title("Results stored at: {}".format(self.experiments_path))
         screen.log_title("Total runtime: {}".format(datetime.datetime.now() - self.time_started))
@@ -273,7 +285,8 @@ class Logger(BaseLogger):
                 screen.error('Experiment name must be composed only of alphanumeric letters, '
                              'underscores and dashes and should not be longer than 100 characters.')
 
-        return match.group(0)
+        self.experiment_name = match.group(0)
+        return self.experiment_name
 
     def get_experiment_path(self, experiment_name, create_path=True):
         general_experiments_path = os.path.join('./experiments/', experiment_name)