Corrects wording on event_window test, with regards to empty values.

These tests ensure that there are three, not two, empty values
at the beginning of the transform.

Also, ensures that we are using a window length of 3 on the tests.
So that wordings of errors,etc. match the window length.
Enriches message returned for test batch transform.

Adds formatting of the failing values when ReturnPriceBatchTransform's
data shape does not match the window_length.
Fixes dates used in test factory for batch transforms.

The test factory was creating non-market days.
i.e. the date range spanned the weekend.

Using pandas' BDay frequency so that only business days are created.

This specific date range doesn't have holidays, so not accounting
for holidays in the factory.

Also, widens the range of the trading calendar to cover the test dates
generated by the factory which include 1990.
Previously the trading calendar began with 2002, meaning that holiday
and weekend adjustments with the data exercised by the factory did
not trigger when run with data in 1990.

This does increase the memory footprint of the tradingcalendar module.
However, only by a couple MB, so taking the hit there to enable
correct behavior.