new_estimates: Estimates Class Constructer function
In chrishaarstick/madstork.opt: MadStork Portfolio Optimization

Creates an estimate object

1 2	new_estimates(symbols, start_date, end_date, grain, periods, prices, returns, mu, sigma, dividends)

`symbols`	vector of security symbols
`start_date`	start date for historical prices
`end_date`	end date for historical prices
`grain`	time grain of returns. Can be either day, week, month, year
`periods`	number of time periods
`prices`	optional input for security prices
`returns`	optional input for security returns
`mu`	optional input for mean estimates
`sigma`	optional input for sigma estimates
`dividends`	optional input for dividend estimates