Avoid creating a new Service object for each API call

[Desrever Nu]

The way we structured the TradeInterface at the moment is not efficient .

We create a new "Service" object for each query.

@Override
    public String query(String base, String method, TreeMap<String, String> args, boolean isGet) {
        PeatioService query = new PeatioService(base, method, args, keys);
        ...