Pass issue bodies and PR base/head branches into templating method (#164)

* Pass issue/PR body to templating method

* Add pr base and head branch refs

Author: kyeah

lib/src/Gren.js

@@ -513,7 +513,10 @@ class Gren {
             labels: this._templateLabels(issue),
             name: issue.title,
             text: '#' + issue.number,
-            url: issue.html_url
+            url: issue.html_url,
+            body: issue.body,
+            pr_base: issue.base && issue.base.ref,
+            pr_head: issue.head && issue.head.ref
         }, this.options.template.issue);
     }