Add documentation for cookies (#116)

* Add cookies to request docs

* Add cookies to response docs

* Reformat the postion of methods

docs/requests.md

@@ -55,6 +55,16 @@ Headers are exposed as an immutable multi-dict.
 
 For example: `request.query_params['abc']`
 
+#### Cookies
+
+Cookies are exposed as an immutable dict.
+
+**Note**: Exception `KeyError` will be raised if nonexistant key is  accessed as `request.cookies['key']`.
+Instead cookies should be accessed with the `.get` method.
+
+For example: `request.cookies.get('mycookie')`
+
+
 #### Body
 
 There are a few different interfaces for returning the body of the request:

docs/responses.md

@@ -30,6 +30,27 @@ class App:
         response = Response('Hello, world!', media_type='text/plain')
         await response(receive, send)
 ```
+#### Set Cookie
+
+Starlette provides a `set_cookie` method to allow you to set cookies on the response object.
+
+Signature: `Response.set_cookie(key, value, max_age=None, expires=None, path="/", domain=None, secure=False, httponly=False)`
+
+* `key` - A string that will be the cookie's key.
+* `value` - A string that will be the cookie's value.
+* `max_age` - An integer that defines the lifetime of the cookie in seconds. A negative integer or a value of `0` will discard the cookie immediately. `Optional`
+* `expires` - An integer that defines the number of seconds until the cookie expires. `Optional`
+* `path` - A string that specifies the subset of routes to which the cookie will apply. `Optional`
+* `domain` - A string that specifies the domain for which the cookie is valid. `Optional`
+* `secure` - A bool indicating that the cookie will only be sent to the server if request is made using SSL and the HTTPS protocol. `Optional`
+* `httponly` - A bool indicating that the cookie cannot be accessed via Javascript through `Document.cookie` property, the `XMLHttpRequest` or `Request` APIs. `Optional`
+
+#### Delete Cookie
+
+Conversly, Starlette also provides a `delete_cookie` method to manually expire a set cookie.
+
+Signature: `Response.delete_cookie(key, path='/', domain=None)`
+
 
 ### HTMLResponse