var mailgunConfig = {
//Your api key, from Mailgun’s Control Panel
api_key : 'MAILGUN-API-KEY',

//Your domain, from the Mailgun Control Panel
domain : 'YOUR-DOMAIN.com',

//Your sending email address
from_who : 'your@email.com'
}

module.exports  = mailgunConfig;
@@ -74,21 +74,40 @@
 y : 
-'MAILGUN-API-
+process.env.API_KEY %7C%7C'YOUR_API_
 KEY'
@@ -168,24 +168,44 @@
 n : 
-'YOUR-DOMAIN.com
+process.env.DOMAIN %7C%7C 'yourdomain.me
 ',%0A%0A
@@ -248,23 +248,50 @@
 o : 
-'your@email.com
+process.env.FROM_WHO %7C%7C 'you@yourdomain.me
 '%0A%7D%0A
@@ -323,8 +323,9 @@
 nConfig;
+%0A

Update mailgun.js to support heroku