add pd.concat replace pd.append

[BryR0]

for error:

https://github.com/AutoViML/Auto_TS/issues/113

'DataFrame' object has no attribute 'append'

replace from: extra_concatenated = extra_concatenated.append(concatenated)

to try: extra_concatenated = extra_concatenated.append(concatenated) except Exception as e: extra_concatenated = pd.concat([extra_concatenated,concatenated])