Move content from CONTRIBUTING.md

source/developers/component_states.markdown

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+---
+layout: page
+title: "Handling states"
+description: "Instructions how to handle states with your component."
+date: 2016-07-01 20:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+---
+
+It is the responsibility of the component to maintain the states of the devices in your domain. Each device should be a single state and, if possible, a group should be provided that tracks the combined state of the devices.
+
+A state can have several attributes that will help the frontend in displaying your state:
+
+- `friendly_name`: this name will be used as the name of the device
+- `entity_picture`: this picture will be shown instead of the domain icon
+- `unit_of_measurement`: this will be appended to the state in the interface
+- `hidden`: This is a suggestion to the frontend on if the state should be hidden
+
+These attributes are defined in [homeassistant.helpers.entity](https://github.com/home-assistant/home-assistant/blob/master/homeassistant/helpers/entity.py#L180).
+

source/developers/component_visibility.markdown

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+---
+layout: page
+title: "Handling visibility"
+description: "Instructions how to handle visibility with your component."
+date: 2016-07-01 20:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+---
+
+Generally, when creating a new entity for Home Assistant you will want it to be a class that inherits the [homeassistant.helpers.entity.Entity](https://github.com/home-assistant/home-assistant/blob/master/homeassistant/helpers/entity.py) class. If this is done, visibility will be handled for you. 
+You can set a suggestion for your entity's visibility by setting the `hidden` property by doing something similar to the following.
+
+```python
+self.hidden = True
+```
+
+This will SUGGEST that the active frontend hides the entity. This requires that the active frontend support hidden cards (the default frontend does) and that the value of hidden be included in your attributes dictionary (see above). The Entity abstract class will take care of this for you.
+
+Remember: The suggestion set by your component's code will always be overwritten by user settings in the configuration.yaml file. This is why you may set hidden to be False, but the property may remain True (or vice-versa).