patch wrong date format

added checks for whether or not options data exists

see previous

updated column names for accessing options expiration time

added option to load and use historical options data stored in sql format

quick update to date format of options chain

a few bug fixes for historical options data

began implementation of historical data-based options pricing model

fixes to how datetimes are parsed in DataFile, how time to expiration is calculated in BlackScholes

hotfix correct the coefficient in the recent update for closing short positions

fixed an issue where the closing order for expired short trades would increase in position size

convert timezone to non-datetime aware but add utc offset

default on-data-update on strategey now returns the same dataframe

initialize underlying dataframe in Data as an empty dataframe

added some debug info for data streams