Test coverage

A list of files with test coverage less then 80%:

• dios/dios/dios.py (29%)
• saqc/lib/tools.py (49%)
• dios/dios/indexer.py (50%)
• saqc/funcs/rolling.py (50%)
• saqc/funcs/pattern.py (51%)
• saqc/lib/ts_operators.py (58%)
• saqc/funcs/outliers.py (60%)
• saqc/funcs/curvefit.py (63%)
• saqc/funcs/drift.py (68%)
• dios/dios/lib.py (69%)
• dios/dios/base.py (69%)
• saqc/funcs/changepoints.py (72%)
• saqc/funcs/flagtools.py (76%)
• saqc/core/core.py (77%)
• saqc/core/flags.py (78%)