Add slide about versioning and cadence

slides/k8s/versions-k8s.md

@@ -1,7 +1,7 @@
 ## Versions installed
 
-- Kubernetes 1.15.3
-- Docker Engine 19.03.1
+- Kubernetes 1.17.1
+- Docker Engine 19.03.5
 - Docker Compose 1.24.1
 
 <!-- ##VERSION## -->
@@ -23,6 +23,10 @@ class: extra-details
 
 ## Kubernetes and Docker compatibility
 
+- Kubernetes 1.17 validates Docker Engine version [up to 19.03](https://github.com/kubernetes/kubernetes/pull/84476)
+
+  *however ...*
+
 - Kubernetes 1.15 validates Docker Engine versions [up to 18.09](https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG-1.15.md#dependencies)
   <br/>
   (the latest version when Kubernetes 1.14 was released)
@@ -40,5 +44,25 @@ class: extra-details
 - "Validates" = continuous integration builds with very extensive (and expensive) testing
 
 - The Docker API is versioned, and offers strong backward-compatibility
+  <br/>
+  (if a client uses e.g. API v1.25, the Docker Engine will keep behaving the same way)
 
-  (If a client uses e.g. API v1.25, the Docker Engine will keep behaving the same way)
+---
+
+## Kubernetes versioning and cadence
+
+- Kubernetes versions are expressed using *semantic versioning*
+
+  (a Kubernetes version is expressed as MAJOR.MINOR.PATCH)
+
+- There is a new *patch* release whenever needed
+
+  (generally, there is about [2 to 4 weeks](https://github.com/kubernetes/sig-release/blob/master/release-engineering/role-handbooks/patch-release-team.md#release-timing) between patch releases,
+  except when a critical bug or vulnerability is found:
+  in that case, a patch release will follow as fast as possible)
+
+- There is a new *minor* release approximately every 3 months
+
+- At any given time, 3 *minor* releases are maintained
+
+  (in other words, a given *minor* release is maintained about 9 months)