Update elwise reduction doc, start rolling reduction doc
Add some notes on the pandas impl
Start rolling reduce reference code
Add some discussion on efficient rolling window kernels
Add simpler example for rolling max, and implement ascending minima

The ascending minima implementation also includes the `minp`
parameter, so that has slightly more work in the algo.
Updates to the docs, mostly removing old stuff
Merge pull request #248 from mwiebe/docs

Updates to the docs, mostly removing old stuff
Merge pull request #233 from mwiebe/rolling_reduce

Rolling reduce design doc
add nth_list
nth_list indexing from csv
WIP CSV indexing
typo in doctest
get util, nth_list is lazy
add coerce_to_ordered

This should be replaced once DyND nd.as_py supports ordered export
csv produces ordered collections
rec-to-row and row-to-rec are idempotent
json yields tuples
tests use tuples
use get in csv
csv._getitem returns concrete result