Accessor for `pd.Series`

[kwinkunks]

As well as the DataFrame accessor, see #36

• Check is_continuous()
• For continuous:
  • Basic stats like df.describe()
  • Outliers
  • Distribution (best fit)
  • Polynomial params to fit normal (Will need new function.)
  • is_correlated()
  • Possible to do something with sklearn.dummy.DummyRegressor? See #57
  • Imbalance metric? See #54
• For categorical:
  • List ordered uniques w supports (Will need new function.)
  • Imbalance metrics
  • Pattern detection, see #58
  • Result of sklearn.dummy.DummyClassifier using fake X. See #57