run.md: --expose does NOT override Dockerfile EXPOSE

run.md states that the operator can override all defaults set in the Dockerfile, and explicitly says that `--expose` overrides the `EXPOSE` instruction. Neither of these are true. An `EXPOSE` instruction cannot be overridden, `--expose` can only add additional exposed ports.

This change fixes the instructions, and also takes the liberty of crisping up the grammar and phrasing in a place or two.

Signed-off-by: Spencer Brown <spencer@spencerbrown.org>

docs/reference/run.md

@@ -21,7 +21,7 @@ executes `docker run`, she starts a process with its own file system,
 its own networking, and its own isolated process tree.  The
 [*Image*](/reference/glossary/#image) which starts the process may define
 defaults related to the binary to run, the networking to expose, and
-more, but `docker run` gives final control to the operator who starts
+more, but `docker run` gives additional control to the operator who starts
 the container from the image. That's the main reason
 [*run*](/reference/commandline/run) has more options than any
 other `docker` command.
@@ -44,10 +44,9 @@ settings affect:
  * runtime constraints on CPU and memory
  * privileges and LXC configuration
  
-An image developer may set defaults for these same settings when they create the
+An image developer may set defaults for these same settings when she creates the
-image using the `docker build` command. Operators, however, can override all
+image using the `docker build` command. Operators can use the `run` options to override most of the
-defaults set by the developer using the `run` options.  And, operators can also
+defaults set by the developer. And, operators can override nearly all the defaults set by the Docker runtime itself.
-override nearly all the defaults set by the Docker runtime itself.
 
 Finally, depending on your Docker system configuration, you may be required to
 preface each `docker` command with `sudo`. To avoid having to use `sudo` with
@@ -973,12 +972,11 @@ or two examples of how to pass more parameters to that ENTRYPOINT:
 ### EXPOSE (incoming ports)
 
 The Dockerfile doesn't give much control over networking, only providing
-the `EXPOSE` instruction to give a hint to the operator about what
+the `EXPOSE` instruction to specify incoming ports that provide services.
-incoming ports might provide services. The following options work with
+The following `run` command options work with container networking:
-or override the Dockerfile's exposed defaults:
 
-    --expose=[]: Expose a port or a range of ports from the container
+    --expose=[]: Expose a port or a range of ports from the container,
-                without publishing it to your host
+                in addition to ports exposed by the `EXPOSE` Dockerfile instruction
     -P=false   : Publish all exposed ports to the host interfaces
     -p=[]      : Publish a container᾿s port or a range of ports to the host
                    format: ip:hostPort:containerPort | ip::containerPort | hostPort:containerPort | containerPort