DOC: warnings from doc-strings for deprecated functions
various warnings we should fix by fixing the doc-strings (e.g. for clip_upper change to using clip in the examples

```
Validate docstrings (GL06, GL07, GL09, SS04, PR03, PR05, EX04)
ci/../scripts/validate_docstrings.py:764: PerformanceWarning: indexing past lexsort depth may impact performance.
  errs, wrns, examples_errs = get_validation_data(doc)
ci/../scripts/validate_docstrings.py:1: FutureWarning: clip_lower(threshold) is deprecated, use clip(lower=threshold) instead
  #!/usr/bin/env python
ci/../scripts/validate_docstrings.py:1: FutureWarning: clip_upper(threshold) is deprecated, use clip(upper=threshold) instead
  #!/usr/bin/env python
ci/../scripts/validate_docstrings.py:2: FutureWarning: Creating a DatetimeIndex by passing range endpoints is deprecated.  Use `pandas.date_range` instead.
  """
ci/../scripts/validate_docstrings.py:2: FutureWarning: Creating a DatetimeIndex by passing range endpoints is deprecated.  Use `pandas.date_range` instead.
  """
ci/../scripts/validate_docstrings.py:1: FutureWarning: Creating a DatetimeIndex by passing range endpoints is deprecated.  Use `pandas.date_range` instead.
  #!/usr/bin/env python
ci/../scripts/validate_docstrings.py:1: FutureWarning: Creating a DatetimeIndex by passing range endpoints is deprecated.  Use `pandas.date_range` instead.
  #!/usr/bin/env python
ci/../scripts/validate_docstrings.py:1: FutureWarning: clip_lower(threshold) is deprecated, use clip(lower=threshold) instead
  #!/usr/bin/env python
ci/../scripts/validate_docstrings.py:1: FutureWarning: clip_upper(threshold) is deprecated, use clip(upper=threshold) instead
  #!/usr/bin/env python
ci/../scripts/validate_docstrings.py:2: FutureWarning: '.reindex_axis' is deprecated and will be removed in a future version. Use '.reindex' instead.
  """
ci/../scripts/validate_docstrings.py:524: DtypeWarning: Columns (0) have mixed types. Specify dtype option on import or set low_memory=False.
  runner.run(test, out=f.write)
ci/../scripts/validate_docstrings.py:2: FutureWarning: Creating a DatetimeIndex by passing range endpoints is deprecated.  Use `pandas.date_range` instead.
  """
ci/../scripts/validate_docstrings.py:2: FutureWarning: Creating a DatetimeIndex by passing range endpoints is deprecated.  Use `pandas.date_range` instead.
  """
ci/../scripts/validate_docstrings.py:1: FutureWarning: Creating a DatetimeIndex by passing range endpoints is deprecated.  Use `pandas.date_range` instead.
  #!/usr/bin/env python
ci/../scripts/validate_docstrings.py:1: FutureWarning: Creating a DatetimeIndex by passing range endpoints is deprecated.  Use `pandas.date_range` instead.
```