DOC: Updating pandas.Interval docstring
Docstring assigned to the Buenos Aires chapter for the sprint.

Hi, I have a few doubts about the changes.

First about the type of the parameters *left* and *right*, it's ok to refer to them as *orderable*?
In the implementation, the constructor takes any pair of objects that satisfy `left <= right` and the comparison returns a boolean value.
 I tried to pass two numpy arrays and it breaks because of ambiguity, but still it's so general that you can even make Intervals of Intervals, sets or booleans. And I believe this is too permissive and prone to error. 

So what it's better, put a warning about this or add an example that is a little more complex and uses this capability (I tried to think one, but nothing came up to my mind).

And last,  validate_docstrings.py returned this error

`2341, in _signature_from_callable 
   'no signature found for builtin type {!r}'.format(obj)) 
ValueError: no signature found for builtin type <class 'pandas._libs.interval.Interval'>
`

Thanks, happy to collaborate.

PS: Given that this is a Cython file I needed to recompile the project to see the changes in the documentation. I mention this because is not in the sprint guide and I don't know if I will able to add it before the event.