Docs updates

@zoni This should be right up your alley.
Am I overlooking something obvious? We could test if we got an empty dict like this, couldn't we?

```python
def configure(self, configuration):
    if configuration is not None and configuration != {}:
        config = dict(chain(CONFIG_TEMPLATE.items(),
                            configuration.items()))
    else:
        config = CONFIG_TEMPLATE
    super(PluginExample, self).configure(config)
```