Extract the shell runner into devtools.

mojo/devtools/common/README.md

Index: mojo/devtools/common/README.md
diff --git a/mojo/devtools/common/README.md b/mojo/devtools/common/README.md
index 656dbd1ded1824bc50f56ce191ccf7d6497cfc67..7db9cb1f32948e9a9aad0276f52c69c2d2ea630a 100644
--- a/mojo/devtools/common/README.md
+++ b/mojo/devtools/common/README.md
@@ -2,31 +2,29 @@
 
 Unopinionated tools for **running**, **debugging** and **testing** Mojo apps.
 
-The repo consists of:
+## Repo contents
 
- - **devtoolslib** - Python module containing the core scripting functionality
-   for running Mojo apps: shell abstraction with implementations for Android and
-   Linux and support for apptest frameworks
- - executable scripts - example embedders of devtoolslib and other utils
+Devtools offer the following tools:
 
-## Embedding devtoolslib
+ - **mojo_shell** - universall shell runner
+ - **debugger** - supports interactive tracing and debugging of a running mojo shell
+ - **remote_adb_setup** - configures adb on a remote machine to communicate with
+   a device attached to the local machine
 
-As devtools carry no assumptions about build system or file layout being used,
-the primary way of using devtools now is to embed the functionality provided by
-**devtoolslib** in a thin wrapper script. For examples, one can refer to mojo's
-[shell
-runner](https://github.com/domokit/mojo/blob/master/mojo/tools/mojo_shell.py)
-and [apptest
-runner](https://github.com/domokit/mojo/blob/master/mojo/tools/apptest_runner.py).
+and a Python scripting library designed for being embedded (devtoolslib).
 
-## Executable scripts
+### Devtoolslib
 
-The set of executable scripts is WIP. We currently offer:
+**devtoolslib** is a Python module containing the core scripting functionality
+for running Mojo apps: shell abstraction with implementations for Android and
+Linux and support for apptest frameworks. The executable scripts in devtools
+are based on this module.
 
- - **debugger** - supports interactive tracing of a running mojo shell and
-   symbolizing android stack traces
- - **remote_adb_setup** - configures adb on a remote machine to communicate with
-   a device attached to the local machine
+As devtools carry no assumptions about build system or file layout being used,
+one can choose to embed the functionality provided by **devtoolslib** in their
+own wrapper, instead of relying on the provided scripts. For examples, one can
+refer to mojo's [apptest
+runner](https://github.com/domokit/mojo/blob/master/mojo/tools/apptest_runner.py).
 
 ## Install
 
@@ -34,7 +32,7 @@ The set of executable scripts is WIP. We currently offer:
 git clone https://github.com/domokit/devtools.git
 ```
 
-## File location
+## Development
 
 The library is canonically developed [in the mojo
 repository](https://github.com/domokit/mojo/tree/master/mojo/devtools/common),