update heroku button for master

Author: awwa

app.json

@@ -6,6 +6,6 @@
     "inbound parse"
   ],
   "website": "http://www.sendgrid.com",
-  "repository": "https://github.com/awwa/sendgrid-ruby/tree/inbound",
+  "repository": "https://github.com/awwa/sendgrid-ruby",
   "logo": "https://uiux.s3.amazonaws.com/2016-logos/email-logo%402x.png"
 }

lib/sendgrid/helpers/inbound/README.md

@@ -67,7 +67,7 @@ Next, send an email to [anything]@inbound.yourdomain.com, then look at the termi
 
 Get a [Heroku](https://www.heroku.com) account.
 
-[![Deploy](https://www.herokucdn.com/deploy/button.svg)](https://heroku.com/deploy?template=https://github.com/awwa/sendgrid-ruby/tree/inbound)
+[![Deploy](https://www.herokucdn.com/deploy/button.svg)](https://heroku.com/deploy?template=https://github.com/awwa/sendgrid-ruby/)
 
 [Setup your MX records.](https://sendgrid.com/docs/Classroom/Basics/Inbound_Parse_Webhook/setting_up_the_inbound_parse_webhook.html#-Setup) Depending on your domain name host, you may need to wait up to 48 hours for the settings to propagate.