Merge pull request TA-Lib#218 from briancappello/fix-abstract-pandas-series

fix TA-Lib#215: using pandas Series with the abstract interface

Author: mrjbq7

talib/_abstract.pxi

@@ -417,7 +417,7 @@ class Function(object):
             series = self.__input_arrays[price_series]
             if __PANDAS_SERIES is not None and \
                     isinstance(series, __PANDAS_SERIES):
-                series = series.values
+                series = series.values.astype(float)
             args.append(series)
         for opt_input in self.__opt_inputs:
             value = self.__get_opt_input_value(opt_input)