Add get_account_fees()

[mkazlauskas]

#172

Implemented for Binance and Coinbase. Didn't find Nash API docs, so for now it will return a not implemented error. I can implement it for Nash if anyone post a link to relevant docs.

I tested this in my personal project for both exchanges (not via cargo test). Not sure how to set up the tests - a lot of tests (including the new tests) failed after adding .env file with my sandbox credentials for Binance.

I'm new to both rust and this project. I'll happily make an required changes.

Note: there are 2 unrelated changes in binance account tests:

• VS code insisted to format this line: let get_price_ticker_request = GetPriceTickerRequest { - it is the only place, so it doesn't seem like my editor config is different than what you guys are using - it may actually be a good change.
• Spelling correction at .expect("Couldn't get acount balances.");

[notdanilo]

@mkazlauskas thanks for the PR. I will review it ASAP

[notdanilo]

As a first though: Nash should also be supported. I will check how to do it.

[notdanilo]

nash-rust needs to implement getAccountVolumes, see https://github.com/nash-io/nash-rust/issues/62