Update CONTRIBUTING.md

Changed the contributing guidelines.

CONTRIBUTING.md

@@ -1,14 +1,39 @@
-# Contributing to Qresp
+# Contributing to the source
 
-Fork the repository and clone.
+Contributions are welcomed via pull requests. Contact the **Qresp** developers before starting work to ensure it meshes well with the planned development direction and standards set for the project.
 
-**Qresp** needs atleast Python version 3.4 and pip
+## Version control
+
+All changes in a pull request should be closely related. Multiple change sets that are loosely coupled should be proposed in separate pull requests. Use a consistent style for writing code. The pull request should be merged in the `develop` branch. 
+
+The respository can be cloned and Qresp can be installed in this way:
 
 ```bash
 $ git clone https://github.com/qresp-code-development/qresp.git
 $ cd qresp/web
 $ pip install -r requirements.txt
 ```
 
-## Running Tests
+Note: **Qresp** needs at least Python 3.4 and pip
+
+## Features
+
+New features should be applicable to a variety of use-cases. The **Qresp** developers can assist you in designing flexible interfaces.
+
+## Testing
+
+Add tests for all new functionality.
 Run `nose2 -v` to run all tests.
+
+## Release
+
+We use [semantic versioning](https://semver.org/), i.e. version labels have the form v`<major>`.`<minor>`.`<patch>`
+
+ - Patch release: v0.0.0 to v0.0.1, only bug fixes
+ - Minor release: v0.0.0 to v0.1.0, bug fixes and new features that maintain backwards compatibility
+ - Major release: v0.0.0 to v1.0.0, bug fixes and new features that break backwards compatibility
+
+# Contributing to the documentation
+
+Comment complex sections of code so that other developers can understand them.
+Add demonstrations of new functionality, e.g. using Jupyter notebooks.