Add contribution guidelines.

CONTRIBUTING.md

@@ -0,0 +1,36 @@
+# Contributing
+
+Your contributions are always welcome!
+
+
+## Guidelines
+
+- Only one list item per commit.
+
+- Only one commit per pull-request.
+
+- List item requirements:
+
+  - Must follow the following template:
+  `- [project-name](http://example.com/) - A short description.`.
+  - Keep descriptions concise, maximum number of characters is 350.
+  - Description must ends with a period.
+
+- Add a section if needed.
+
+  - Eventually add a description to the section.
+  - Section title must be linked to from the [Table of
+  Contents](README.md#contents).
+
+- Search past and current issues and pull-requests for previous suggestions
+before making a new one, as yours may be a duplicate or a work in progress.
+
+- Check your spelling and grammar.
+
+- Remove any trailing whitespaces.
+
+- Use spaces, no tabs, for indention.
+
+- Try to cut long lines of text after 80 characters.
+
+- Send a pull-request with the reason why the library is awesome.

README.md

@@ -135,6 +135,12 @@ falsehoods are also welcome in this page.
 - [Falsehoods programmers believe about versions](https://github.com/xenoterracide/falsehoods/blob/master/versions.md)
 
 
+## Contributing
+
+Your contributions are always welcome! Please take a look at the [contribution
+guidelines](CONTRIBUTING.md) first.
+
+
 ## License
 
 Content of this repository is licensed under the [BSD 2-Clause