lifecycle: Mention runtime.json

As discussed earlier [1,2].  I'm in favor of rolling it back into
config.json [3], but we aren't there yet [4].

[1]: opencontainers#231 (comment)
[2]: https://github.com/opencontainers/specs/pull/231/files#r46735828
[3]: https://groups.google.com/a/opencontainers.org/forum/#!topic/dev/0QbyJDM9fWY
     Subject: Single, unified config file (i.e. rolling back specs#88)
     Date: Wed, 4 Nov 2015 09:53:20 -0800
     Message-ID: <[email protected]>
[4]: https://github.com/opencontainers/specs/blob/4a63e81a807edec3d67ed2b6bd99a6c2b288676f/bundle.md#container-format

Signed-off-by: W. Trevor King <[email protected]>

runtime.md

@@ -38,8 +38,8 @@ This is provided so that consumers can find the container's configuration and ro
 The lifecycle describes the timeline of events that happen from when a container is created to when it ceases to exist.
 
 1. OCI compliant runtime is invoked by passing the bundle path as argument.
-2. The container's runtime environment is created according to the configuration in config.json.
-   Any updates to config.json after container is running do not affect the container.
+2. The container's runtime environment is created according to the configuration in `config.json` and `runtime.json`.
+   Any updates to `config.json` or `runtime.json` after container is running do not affect the container.
 3. The container's state.json file is written to the filesystem.
 4. The prestart hooks are invoked by the runtime.
    If any prestart hook fails, then the container is stopped and the lifecycle continues at step 8.