fix run variable undefined $api by mxgrim

Merge pull request ccxt#294 from alipjxhub/patch-1

Add trade fee function

Supports network option in withdraw function by mtb-pro

private methods are now protected by lnogueak

Fixing __call for non api functions + Access Binance response headers…

… about x-mbx-used-weight and x-mbx-used-weight-1m

fix memory leak, remove query_logs

Pull requests are welcome.

Withdraw transactionFeeFlag by max-grim

Fix key sanity check by r3bers

fix numberOfDecimals by max-grim