stats: reformat file and fix some help messages

stats.py

@@ -140,7 +140,7 @@ class StatsRunner(object):
         df['Percent'] = df['count'] / df['count'].sum() * 100
         df = df[['user', 'count', 'Percent']]
         df.columns = ['User', 'Total Messages', 'Percent']
-        df['User'] = df['User'].str.replace(r'[^\x00-\x7F]', "", regex=True)
+        df['User'] = df['User'].str.replace(r'[^\x00-\x7F]', "", regex=True)  # Drop emoji
 
         text = df.iloc[:n].to_string(index=False, header=True, float_format=lambda x: f"{x:.1f}")
 
@@ -364,7 +364,8 @@ class StatsRunner(object):
 
         return None, bio
 
-    def get_message_history(self, user: Tuple[int, str] = None, averages: int = None, start: str = None, end: str = None)\
+    def get_message_history(self, user: Tuple[int, str] = None, averages: int = None, start: str = None,
+                            end: str = None) \
             -> Tuple[None, BytesIO]:
         """
         Make a plot of message history over time
@@ -466,7 +467,7 @@ class StatsRunner(object):
             raise HelpException("corr must be either pearson or spearman")
 
         if not 0 <= thresh <= 1:
-            raise HelpException(f'n must be greater than 0, got: {n}')
+            raise HelpException(f'n must be in the range [0, 1], got: {n}')
 
         query = f"""
                 SELECT msg_time, extract(ISODOW FROM msg_time) as dow, extract(HOUR FROM msg_time) as hour,