read_csv could support chunking by contigous values??
Just a thought to investigate further?

Instead of specifiying chunksize, could give column or columns and it could split when these values change.

e.g. 
Say I have a dataset, I know is sorted by date, and there are a lot of records for each date.
I could specify to read_csv to iterate on date, and it will read all rows where date's value are the same and adjacent it each "chunk".

Like I said, not sure how feasible it is, but could be really useful.
