new_gains: Realized Gains Constructor function
In chrishaarstick/madstork: MadStork Portfolio Management

Creates new object of class gains

1 2	new_gains(symbol, quantity, purchase_date, purchase_price, sale_date, sale_price, gain, type)

`symbol`	symbol ticker. character type
`quantity`	number of shares. numeric type
`purchase_date`	date of purchase. Date type
`purchase_price`	cost basis. numeric type
`sale_date`	date of sale. Date type
`sale_price`	sale price
`gain`	gain amount. numeric type
`type`	gain type. short or long term types. character type