logger argument was added

Author: DohanKim

README.md

@@ -10,8 +10,9 @@ Use the code at your OWN risk.
 ## Usage
 
 ```ruby
-bithumb_api = Bithumb.new(bithumb_keys['API_KEY'], bithumb_keys['SECRET_KEY'])
-coinone_api = Coinone.new(coinone_keys['API_KEY'], coinone_keys['SECRET_KEY'])
+logger = Logger.new
+bithumb_api = Bithumb.new(bithumb_keys['API_KEY'], bithumb_keys['SECRET_KEY'], logger)
+coinone_api = Coinone.new(coinone_keys['API_KEY'], coinone_keys['SECRET_KEY'], logger)
 
 p bithumb_api.balance('eos')
 p coinone_api.balance('eos')