BUG: Algo no longer crashes after creating new history column.

Fixes an issue that caused a crash if a user assigned a new column into a
returned history DataFrame.  This occurred because we re-use DataFrames between
history() calls, so the new column caused an index-size mismatch on the next
attempted calculation.

Ideally we would fix this by in-place dropping the columns, but that isn't
supported in pandas 0.12.0, so instead we just return a complete copy of the
frame.  We should re-evaluate this implementation when we're on a more modern
pandas version.
ENH: Added dynamic name functionality to record() API function.

Added the ability to pass *args before the **kwargs so that positional
arguments of the form name, value can be recorded.
BUG: Fix constant of trading hours to be 6.5. Fixes #214.
MAINT: Removed undocumented and untested sources for pytables and csv. Closes #267.
Update zipline-0.6.2.md

Added a note about record functionality.
Update zipline-0.6.2.md
Update zipline-0.6.2.md
ENH: Added informative message for calling order in init.

Previously, calling order() in initalize resulted in a weird
stack trace. It now returns a well formulated error that is
readable to the user through the API. Adding a slippage
kwarg to test_algorithm and simfactor was necessary because
slippage can only be called during init. Previously initaliazed
was never set to true and calls to init-only function were sprinkled
around the code in non-init sections. Code changes were to enforce
init-only rules.
ENH: Implemented AUTO_INITIALIZE feature.

Created a new flag in TradingAlgorithm that enables subclasses to
decide if they want to handle setting self.initialized = True.
Before it was the responsibility of an overriding subclass to set
initalized = True. This was causing problems because it's easy to
forget this. Now it is the responsibility of TradingAlgorithm
unless explicity stated otherwise.
MAINT: Remove redundant perf_tracker member.

The perf_tracker member of TradingMember was set to None twice
during __init__.

Remove one of those instances.
ENH: Change open and close to midnight if using daily input data.
MAINT: Factor out column conversion in HistoryContainer.

We can't be sure that security identifiers can be converted
to int. In fact, most of the times they are strings. This
adds an identity function that can be overwritten if such
a conversion is necessary (as on Quantopian).
TST: Add unittest for daily history with midnight dt.