Upgrade pytz
Changes test sources to use unit test's assert instead of plain assert.
Changes test factory to use Event instead of ndict.

As more sources are moving off of ndict,
changing the factory to use Event, so that when testing we are
exercising use of Event.
Changes type emitted from DataSource to Event.

Moving DataSource to Event for improvements in member access
and setting.
Uses dictionary update instead of iterating through keys.

update_universe is a bottleneck on large data sets.

A large portion of that bottleneck is the call to getitem while
looping over the keys, so using update while passing along the internal
__dict__

Seeing about a 40% improvement.
Changes date_sort to use heapq module.

Uses heapq.merge to sort input from mulitple sources instead of
our own sort module.

From profiling heapq.merge is more efficient than our own efforts.
Removes sort module.

Sort module is now unneeded with use of heapq.merge

Also adapts test_perf_tracking so that it uses date_sorted_sources.
Removes done message.

Instead of checking for 'DONE' on each call uses generators
builtin StopIteration for signalling the end of input.
ENH: batch_transform now supports sid-filtering. DOC: Added docs to batch_transform.
ENH: batch_transform now supports field filtering.
ENH: sid and field filter kwargs can also be strings or ints.
ENH: Added new kwarg to batch_transform: create_panel.
ENH: New batch_transform feature: compute_only_full.
MIN: Changed isinstance check to allow more types.
Adds _ prefix to decorate_source to imply internal usage.
Merge pull request #53 from quantopian/performance-improvements-sorting-and-done-message

Performance improvements sorting and done message
DOC: Typo.
Merge pull request #54 from quantopian/enhance_batch_full_panel

Enhance batch full panel
Uses a Portfolio object instead of an ndict.

Gains some performance by using a 'regular' object instead of
an ndict.

Also, directly sets up the values that we return, instead of going in
between with __core_dict and then removing values.

In it's entirety performanc.as_portfolio is the current
highest bottleneck, working on reducing time spent in that function.