Uses YAHOO financial rates and symbols from localeplanet.com. If it can't connect, uses local copy in 'rates.json'.
Params:
--amount amount of currency to be exchanged
--input_currency code or symbol of currency to be achanged
--output_currency code or symbol of currency to exchange to (if not provided will convert to all known currencies)
Output is json object writen in console and to file 'exchanged.json'.
note: If you use symbol that matches more currencies, it converts to them all. Caution: If symbol is used at input, will create list of JSON objects for each of matching pair symbol - code!