Revised the connect method

When there was an error with the request, the connect method was returning the string
"Connection refused". This would cause errors in the subclasses. So I have it printing the string and
then exiting. I think in the future exceptions should be used.

Author: taylorjdawson

etherscan/client.py

@@ -82,7 +82,9 @@ def connect(self):
         try:
             req = self.http.get(self.url)
         except requests.exceptions.ConnectionError:
-            return "Connection refused"
+            print("Connection refused")
+            exit()
+            
         if req.status_code == 200:
             # Check for empty response
             if req.text: