Causal Impact failing due to to pandas update

[Simha-Kalimipalli]

Causal impact is failing recently due to this error:

module 'pandas.core.dtypes.common' has no attribute 'is_date_time_or_time_delta_type'

Pandas seems to have removed is_date_time_or_time_delta_type as I can not find it here: https://github.com/pandas-dev/pandas/blob/main/pandas/core/common.py

[aurel-p]

Same problem here

[causalkayak]

Have an open PR to fix that issue here: #50