Improve i_batch

Add grouper from the example on itertools docs

Add batcher and i_batcher
 based on grouper while filtering out the fill value
Add i_batch tests
Reverse batcher arg order.

With two positional args, having the iterable second
supports more cases to use it in conjuction with
functools.partial.
Remove grouper and grouper based batchers

I prefer to not use the filter fill value method to
batch. I don't like the need to allocate room for
the fill value object.
Merge pull request #10 from johnwlockwood/i_batch

I batch
Merge branch 'development' into buffering