Use the master branch as default for heroku deployments

Devel might contain instable features

README.md

@@ -18,7 +18,7 @@ that by providing one-click installation on Heroku or
 [Sandstorm](https://sandstorm.io) platforms and verified
 [Docker](https://www.docker.com) images.
 
-[![Deploy](https://www.herokucdn.com/deploy/button.png)](https://heroku.com/deploy)
+[![Deploy](https://www.herokucdn.com/deploy/button.png)](https://heroku.com/deploy?template=https://github.com/wekan/wekan/tree/master)
 
 Wekan is released under the very permissive [MIT license](LICENSE), and made
 with [Meteor](https://www.meteor.com).

app.json

@@ -2,7 +2,7 @@
   "name": "Wekan",
   "description": "The open-source Trello-like kanban",
   "repository": "https://github.com/wekan/wekan",
-  "logo": "https://raw.githubusercontent.com/wekan/wekan/heroku/meta/icons/wekan-150.png",
+  "logo": "https://raw.githubusercontent.com/wekan/wekan/master/meta/icons/wekan-150.png",
   "keywords": ["productivity", "tool", "team", "kanban"],
   "website": "http://wekan.io",
   "env": {