Fix helper mail_example redirection link

Joshua de Guzman · web-flow · commit fe4f43b3554e · 2018-10-08T19:36:58.000+08:00
diff --git a/README.md b/README.md
@@ -84,7 +84,7 @@ pip install sendgrid
 
 ## Hello Email
 
-The following is the minimum needed code to send an email with the [/mail/send Helper](https://github.com/sendgrid/sendgrid-python/tree/master/sendgrid/helpers/mail) ([here](https://github.com/sendgrid/sendgrid-python/blob/master/examples/helpers/mail/mail_example.py#L20) is a full example):
+The following is the minimum needed code to send an email with the [/mail/send Helper](https://github.com/sendgrid/sendgrid-python/tree/master/sendgrid/helpers/mail) ([here](https://github.com/sendgrid/sendgrid-python/blob/master/examples/helpers/mail_example.py) is a full example):
 
 ### With Mail Helper Class
 
