MAINT: Factored out _create_data_generator helper method
MAINT: Specify --use-mirrors to pip install
MAINT: Move search day distance function to module level.
MAINT: Move get_treasury_rate to risk module level.
MAINT: Factor out start and end date choose_treasury parameters.

Preparing for move of method to a module level function.
MAINT: Remove saving of treasury duration.

The treasury_duration member in RiskMetrics is never used except
for in unit tests.

Remove the saving of treasury_duration in preparation for the
move of the choose_treasury method out of the RiskMetrics classes.

Down the line, if we do restore the sanving of treasury_duration,
choose_treasury can return a tuple that includes treasury_duration
instead of just returning the rate.
MAINT: Factor out treasury_curve argument from risk choose_benchmark

Move the reference to self.treasury_curve to a parameter, on the path
of making this method a module level function.
MAINT: Move choose_treasury method from risk metrics class to module.
MAINT: Refactors out selection of treasury duration its own function.

Instead of having the duration selection logic in choose_treasury,
break out duration specific logig into another function.
MAINT: Mask treasury_curves used by risk metrics to period range.

So that calculations that leverage the range of the treasury_curves,
like `pd.Series.searchsorted` will not overshoot the 'end' of the
range we are calculating risk metrics.
MAINT: Use searchsorted instead of bisect on treasury curves.

Remove use of .keys() and creation of a new list of the curve
Series's values.
Merge move of risk module treasury curve methods to module functions.

Intent is to both make the inputs to the treasury curve logic
more clear/explicit, as well as reducing the responsibilities
of the RiskMetrics classes.

Functions to move:
- search_day_distance
- get_treasury_rate
- choose_treasury

Also add new function:
- select_treasury_duration, split out of choose_treasury
MAINT: Add --use-mirrors to Travis CI build script
MAINT: PyPI upgrade mccabe==0.2.1
BUG: Fix tradesimulation index into perf results when emitting minutely.

The indexing into performance results during the simulation loop fails
when emitting minutely since 'daily_perf' only exists on daily performance
results, not the minutely results.

Fix by making the key used to index into performance results depend
on the emission rate.
DEV: Add note about running tests to README
DEV: Add notes on dependency installation to README
BUG: Preseve docstring in batch functions

The batch_transform decorator wipes out the doc string of the function
it wraps. Decorate the creator with functools.wraps to preserve function
metadata.
REL: Updates copyright on transforms.utils module.
BUG: Stop intraday performance from emitting all transactions.

The intraday performance results were emitting all transactions
for the entire day up to that point, instead of the desired transaction
list for the current timestamp.

Add a `dt` parameter to the `to_dict` method of PerformancePeriod so
that the transactions are limited to a specific datetime.
When the parameter is `None`, a todays_performance object will
function as previously with returning all transactions for the day.
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