chaikin_oscillator fix

Fix for Chaikin Oscillator as suggested by @renubar

indicators.py

@@ -224,13 +224,15 @@ def bollinger_bands(data, trend_periods=20, close_col='<CLOSE>'):
 def chaikin_oscillator(data, periods_short=3, periods_long=10, high_col='<HIGH>',
                        low_col='<LOW>', close_col='<CLOSE>', vol_col='<VOL>'):
     ac = pd.Series([])
-
+    val_last = 0
+
     for index, row in data.iterrows():
         if row[high_col] != row[low_col]:
-            val = ((row[close_col] - row[low_col]) - (row[high_col] - row[close_col])) / (row[high_col] - row[low_col]) * row[vol_col]
+            val = val_last + ((row[close_col] - row[low_col]) - (row[high_col] - row[close_col])) / (row[high_col] - row[low_col]) * row[vol_col]
         else:
-            val = 0
+            val = val_last
         ac.set_value(index, val)
+	val_last = val
 
     ema_long = ac.ewm(ignore_na=False, min_periods=0, com=periods_long, adjust=True).mean()
     ema_short = ac.ewm(ignore_na=False, min_periods=0, com=periods_short, adjust=True).mean()