Moved from the `lazy-mainline` branch,
https://github.com/quantopian/zipline/pull/858
The intent of this patch to provide the basic class and readers
interfaces, developed on that branch, so that the use of creating the
object and opening paths etc. can be tested internally.
Additional changes beyond the lazy-mainline branch, addition of future
minute reader, and daily bar reader.
Also allow an argument of the future_daily_reader, though no such reader
yet exists.
It may be that future and equity readers share an interface, and a
further improvement would be providing an abstract base class.
co-author: @jbredeche <jean@quantopian.com>