ENH: Added DataPanelSource.
Updates to the latest version of Cython.
Removes Cython from requirements list.

zipline doesn't need Cython in stand alone mode.
Forward-fill missing treasury data

To handle, for instance, Columbus Day (Oct 10),
on which there is no treasury data.

We're only forward-filling data now, and
no longer searching both back and forward in time.
Merge pull request #45 from quantopian/handle_no_treasury_data

Forward-fill missing treasury data
Updates requests to newest release. (1.0.0)
Updates pandas to the latest version. 0.9.1 --> 0.10.0
Release 0.5.5

Salient changes since last version:

- Adds non-holiday closings to trading calendar.
- Forward filling of missing treasury data.
- Improves handling of treasury data when the backtest's
  end date day is not a market day.
- Adds option to forward fill data in batch transform.
Moves requests to main requirements. Also upgrades to 1.0.3

Moving to main requirements, since zipline will not run without
the treasury and benchmark data that we requests to fetch.

Upgrade is to keep current with latest release.
Merge pull request #43 from quantopian/extend_df_source

ENH: Added DataPanelSource.
BUG: Adding of new fields to data panel source should be inside of if-statement.
Handles the case where pandoc isn't available during download.

Also bumps version up to 0.5.6 so the new version will apply.
Updates README example code to use window_length instead of days.

In a previous patch, the transform argument had been changed
from days to window_length.

The README example was thus not able to be run, updating algo
so that it runs against current versions of transforms.
ENH: Add granularity and annualizer arguments to TradingAlgorithm. Accompanying doc string and unittest.
MIN: Replaced annualizer with a dictionary. Added set_granularity method.
Changes tests from using an ndict for trades to an Event object.

When run over large amounts of data the use of ndict's gets and sets
become a large bottleneck, around 1/5th of the CPU time is spent
in ndict's __setattr__, __getattr__, etc.

By switching to an object for an event,
we reduce the penalty significantly.

Removes asserts that check for event being an ndict, as well as those
that assume a certain behavior of the __contains__ method for events.
Merge pull request #48 from quantopian/change-trade-from-ndict-to-object-based-event

Changes tests from using an ndict for trades to an Event object.
Optimizes checking ready state of sources during sorting.

The main bottle neck here was using `len`.
A boolean check is a sufficient test for more items in the queue.

Also, uses all instead of several functions.
Adds a __repr__ method for Event.
Removes assert of message confirming to protocol.

Two reasons for removal:
- On the path of removing most non-postconditional asserts.
  Since the asserts on every message is incurring a
  non-insignificant penalty on large datasets.
- Since the assert was invoked as a function, the 'right side'
  of the assert statement, i.e. the error message was being invoked
  as a function, discovered since the __repr__ of the message was
  high on the bottleneck list.