docs: Add Python API usage example

Fixes: #297

docs/development.rst

@@ -2,7 +2,17 @@ Development
 ===========
 
 yamllint provides both a script and a Python module. The latter can be used to
-write your own linting tools:
+write your own linting tools.
+
+Basic example of running the linter from Python:
+
+.. code-block:: python
+
+   import yamllint
+
+   yaml_config = yamllint.config.YamlLintConfig("extends: default")
+   for p in yamllint.linter.run("example.yaml", yaml_config):
+       print(p.desc, p.line, p.rule)
 
 .. automodule:: yamllint.linter
    :members: