Update Swarm documentation

Signed-off-by: Joffrey F <joffrey@docker.com>

docs/swarm.md

-# Using swarm for API version 1.24 or higher
+# Swarm management
 
-Swarm initialization is done in two parts.  Provide a listen_addr and `force_new_cluster` (OPTIONAL) to
-the `Client().swarm_init()` method, and declare mappings in the
-`swarm_opts` section.
+Starting with Engine version 1.12 (API 1.24), it is possible to manage the
+engine's associated Swarm cluster using the API.
+
+## Initializing a new Swarm
+
+You can initialize a new Swarm by calling `Client.init_swarm`. An advertising
+address needs to be provided, usually simply by indicating which network
+interface needs to be used. Advanced options are provided using the
+`swarm_spec` parameter, which can easily be created using
+`Client.create_swarm_spec`.
 
 ```python
-swarm_id = cli.swarm_init(listen_addr="0.0.0.0:4500", 
-swarm_opts={
-  "AcceptancePolicy": {
-    "Policies": [
-      {
-        "Role": "MANAGER",
-        "Autoaccept": True
-      }
-    ]
-  }
-})
+spec = client.create_swarm_spec(
+  snapshot_interval=5000, log_entries_for_slow_followers=1200
+)
+client.init_swarm(
+  advertise_addr='eth0', listen_addr='0.0.0.0:5000', force_new_cluster=False,
+  swarm_spec=spec
+)
 ```
 
-Join another swarm, by providing the remote_address, listen_address(optional), 
-secret(optional), ca_cert_hash(optional, manager(optional)
+## Joining an existing Swarm
+
+If you're looking to have the engine your client is connected to joining an
+existing Swarm, this ca be accomplished by using the `Client.join_swarm`
+method. You will need to provide a list of at least one remote address
+corresponding to other machines already part of the swarm. In most cases,
+a `listen_address` for your node, as well as the `secret` token are required
+to join too.
+
 ```python
-cli.swarm_join(
-    remote_address="swarm-master:2377",
-    manager=True     
+client.join_swarm(
+  remote_addresses=['192.168.14.221:2377'], secret='SWMTKN-1-redacted',
+  listen_address='0.0.0.0:5000', manager=True
 )
 ```
 
+## Leaving the Swarm
+
+To leave the swarm you are currently a member of, simply use
+`Client.leave_swarm`. Note that if your engine is the Swarm's manager,
+you will need to specify `force=True` to be able to leave.
+
+```python
+client.leave_swarm(force=False)
+```
+
+
+## Retrieving Swarm status
 
-Leave swarm 
+You can retrieve information about your current Swarm status by calling
+`Client.inspect_swarm`. This method takes no arguments.
 
 ```python
-cli.swarm_leave()
+client.inspect_swarm()
 ```
+
+## Swarm API documentation
+
+### Client.init_swarm
+
+#### Client.create_swarm_spec
+
+#### docker.utils.SwarmAcceptancePolicy
+
+#### docker.utils.SwarmExternalCA
+
+### Client.inspect_swarm
+
+### Client.join_swarm
+
+### CLient.leave_swarm
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