Add the smoothing utility class

* implements the existing smoothers found in the indicators (window average, gaussian local linear regression)
* adds the more general Savitzky-Golay filter as 'savgol' with gaussian weighting
* adds imputation options
* adds tests to match

Author: dshemetov

_delphi_utils_python/delphi_utils/__init__.py

@@ -7,6 +7,8 @@
 from .archive import ArchiveDiffer, GitArchiveDiffer, S3ArchiveDiffer
 from .export import create_export_csv
 from .utils import read_params
+
 from .geomap import GeoMapper
+from .smooth import Smoother
 
 __version__ = "0.1.0"