Allow posting comments by replying to an email with Griddler gem

As you’re probably aware, SendGrid is great at sending your email, but SendGrid can also help you process email using the Inbound Parse Webhook. The Inbound Parse Webhook processes all incoming email for a domain or subdomain, parses the contents and attachments of that email, then POSTs the multipart/form-data of the attachment and JSON-encoded content to the URL of your choosing. To send an email to the application we use sendgrid services. Sendgrid provides different APIs for different purposes. For incoming email processing use inbound parse webhook API. The API says that: The Parse API will POST the