ENH: Provides a more descriptive error if market_open or market_close are provided a non-keyword argument that is not a datetime.timedelta
ENH: Provides aliases for the (Date|Time)RuleFactory classes for better Quantopian/Zipline interoperability
ENH: Changes the default time_rule for schedule_function to market_open()
BUG: Fixed a bug with offsets in week_start and week_end
ENH: Does value checking for time offsets for market_open and market_close