README.md in rumble-0.3.7 vs README.md in rumble-0.4.0

@@ -43,18 +43,28 @@
 ```
 
 The list of emails must contain three columns separated by a comma: first
 name, last name, and email.
 
-## How to contribute?
+# How to contribute
 
-Just submit a pull request. Make sure `rake` passes.
+Read [these guidelines](https://www.yegor256.com/2014/04/15/github-guidelines.html).
+Make sure you build is green before you contribute
+your pull request. You will need to have [Ruby](https://www.ruby-lang.org/en/) 2.3+ and
+[Bundler](https://bundler.io/) installed. Then:
 
+```
+$ bundle update
+$ rake
+```
+
+If it's clean and you don't see any error messages, submit your pull request.
+
 ## License
 
 (The MIT License)
 
-Copyright (c) 2018 Yegor Bugayenko
+Copyright (c) 2018-2019 Yegor Bugayenko
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the 'Software'), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell