runtime: Add post-stop hooks to the lifecycle

These just landed via opencontainers#202.  I'm not entirely clear on how we intend
to handle "the application died before we finished executing post-stop
hooks", but I've made my best guess here.

Signed-off-by: W. Trevor King <wking@tremily.us>

runtime-config.md

@@ -26,7 +26,7 @@ If a hook returns a non-zero exit code, [then an error including the exit code a
 
 ### Post-start
 
-The post-start hooks are called after the user process is started.
+The post-start hooks are called [after the user process is started](runtime.md#typical-lifecycle).
 For example this hook can notify user that real process is spawned.
 
 If a hook returns a non-zero exit code, then an error is logged and the remaining hooks are executed.

runtime.md

@@ -39,17 +39,18 @@ A typical lifecyle progresses like this:
 4. The runtime executes any [pre-start hooks](runtime-config.md#pre-start)
 5. The runtime [executes the container process](#start-process)
 6. The container process is running
-7. A user tells the runtime to send a termination signal to the container process
-8. The runtime [sends a termination signal to the container process](#stop-process)
-9. The container process exits
-10. The runtime [terminates any other processes in the container](#stop-process)
-11. The runtime executes any [post-stop hooks](runtime-config.md#post-stop)
-12. The runtime [removes the container](#cleanup)
+7. The runtime executes any [post-start hooks](runtime-config.md#post-start)
+8. A user tells the runtime to send a termination signal to the container process
+9. The runtime [sends a termination signal to the container process](#stop-process)
+10. The container process exits
+11. The runtime [terminates any other processes in the container](#stop-process)
+12. The runtime executes any [post-stop hooks](runtime-config.md#post-stop)
+13. The runtime [removes the container](#cleanup)
 
 With steps 7 and 8, the user is explicitly stopping the container process (via the runtime), but it's also possible that the container process could exit for other reasons.
-In that case we skip directly from 6 to [10](#stop-process).
+In that case we skip directly from 6 to [10](#stop-process), skipping any post-start hooks that hadn't been launched and terminating any in-progress post-start hook.
 
-Failure in a pre-start hook or other setup task can cause a jump straight to [11](runtime-config.md#post-stop).
+Failure in a pre-start hook or other setup task can cause a jump straight to [12](runtime-config.md#post-stop).
 
 ### Create