an important fix connected to the Conf method

[maxim-dzh]

Description:

1. After this call of the "Conf" method, the "currenciesConf" slice will be always empty, because the "parseExchangeMap" method doesn't add a new config to the common map

   currenciesConf, err := client.Currencies.Conf(false, false, false, false, true)
   if err != nil {
   return nil, err
   }

2. The "Conf" method creates the "parsedRaw" slice with the specified length, but afterward, new elements are added by "append". As result, we have redundant empty elements in the "parsedRaw" slice.

Breaking changes:

-

New features:

Fixes:

• [x] currencies configuration fix

PR status:

• [ ] Version bumped
• [ ] Change-log updated