Added Relay basic documentation

Author: syrusakbary

docs/config.toml

@@ -14,4 +14,5 @@ siteTitle = "Graphene"
 	  "/docs/objecttypes/",
 	  "/docs/mutations/",
 	  "/docs/basic-types/",
+	  "/docs/relay/",
 	]

docs/pages/docs/relay.md

@@ -0,0 +1,63 @@
+---
+title: Relay
+description: A Relay implementation in Graphene
+---
+
+# Relay
+
+Graphene have complete support of [Relay](https://facebook.github.io/relay/docs/graphql-relay-specification.html), and it offers some utils for working if from Python easy.
+
+## Nodes
+
+A `Node` is an Interface provided by `graphene.relay` that contains a single field `id` (which is a `ID!`). Any object that inherits from it have to implement a `get_node` method for retrieving a `Node` by an *id*.
+
+Example usage (taken from the [Starwars Relay example](https://github.com/graphql-python/graphene/blob/master/examples/starwars_relay/schema.py)):
+
+```python
+class Ship(relay.Node):
+    '''A ship in the Star Wars saga'''
+    name = graphene.String(description='The name of the ship.')
+
+    @classmethod
+    def get_node(cls, id, info):
+        return get_ship(id)
+```
+
+The `id` returned by the `Ship` type when you query it will be a scalar which contains the enough info for the server for knowing it's type and it's id.
+
+For example, the instance `Ship(id=1)` will return `U2hpcDox` as the id when you query it (which is the base64 encoding of `Ship:1`), and which could be useful later if we want to query a node by its id.
+
+
+## Connection
+
+A connection is a vitaminized version of a List that provides ways of slicing and paginating through it. The way you create Connection fields in `graphene` is using `relay.ConnectionField`.
+
+You can create connection fields in any ObjectType, but the connection **must** be linked to an object which inherits from `Node` (in this case, a `Ship`).
+
+```python
+class Faction(graphene.ObjectType):
+    name = graphene.String()
+    ships = relay.ConnectionField(Ship)
+
+    def resolve_ships(self, args, info):
+        return []
+```
+
+## Node Root field
+
+As is required in the [Relay specification](https://facebook.github.io/relay/graphql/objectidentification.htm#sec-Node-root-field), the server must implement a root field called `node` that returns a `Node` Interface.
+
+For this reason, `graphene` provides the field `relay.NodeField`, which links to any type in the Schema which inherits from `Node`. Example usage:
+
+```python
+class Query(graphene.ObjectType):
+    node = relay.NodeField()
+```
+
+
+## Useful links
+
+* [Getting started with Relay](https://facebook.github.io/relay/docs/graphql-relay-specification.html)
+* [Relay Global Identification Specification](https://facebook.github.io/relay/graphql/objectidentification.htm)
+* [Relay Cursor Connection Specification](https://facebook.github.io/relay/graphql/connections.htm)
+* [Relay input Object Mutation](https://facebook.github.io/relay/graphql/mutations.htm)