See public hub at https://hub.docker.com/r/rsvp/fecon235
regarding running our Docker container.

Move and rewrite ema() to close #5
since *pd.ewma() is deprecated* as of pandas 0.18.
Our old ema() has been commented out in lib/yi_1tools.py
then new ema() has been rewritten in lib/yi_timeseries.py
as a special case of holtlevel().
See issue #5 for details on pandas deprecation warning,
Exponential Moving Average and Holt-Winters smoothing:
https://github.com/rsvp/fecon235/issues/5