Conflicting documentation about index uniqueness
The page http://pandas.pydata.org/pandas-docs/dev/generated/pandas.Series.html says:

> index : array-like or Index (1d)
> Values must be unique and hashable, same length as data. 

A little bit earlier the same page says: 

> Labels need not be unique but must be any hashable type.  

Other pages also mention non-unique index support (e.g. http://pandas.pydata.org/pandas-docs/dev/dsintro.html) It looks like `index` description should read:

> index : array-like or Index (1d)
> Values must be hashable, same length as data. Non-unique index values are allowed. 
