Update docs describing what the installers do

doc/installers.rst

@@ -3,24 +3,25 @@ Installer details
 
 The installers pynsist builds do a number of things:
 
-1. Unpack and run the Python .msi installer for the version of Python you
-   specified.
-2. Unpack and run the .msi installer for the `py launcher
-   <https://bitbucket.org/vinay.sajip/pylauncher>`_, if you're using Python 2
-   (in Python 3, this is installed as part of Python).
-3. Install a number of files in the installation directory the user selects:
+1. Install a number of files in the installation directory the user selects:
 
+   - An embedded build of Python, including the standard library.
+   - A copy of the necessary Microsoft C runtime for Python to run, if this
+     is not already installed on the system.
    - The launcher script(s) that start your application
    - The icon(s) for your application launchers
    - Python packages your application needs
    - Any other files you specified
 
-4. Create a start menu shortcut for each launcher script. If there is only one
+2. Create a start menu shortcut for each launcher script. If there is only one
    launcher, it will go in the top level of the start menu. If there's more than
    one, the installer will make a folder named after the application.
+3. If you have specified any :ref:`commands <command_config>`, modify the
+   :envvar:`PATH` environment variable in the registry, so that your commands
+   will be available in a system command prompt.
+4. Byte-compile all Python files in the ``pkgs`` subdirectory. This should
+   slightly improve the startup time of your application.
 5. Write an uninstaller, and the registry keys to put it in 'Add/remove programs'.
-   The uninstaller only uninstalls your application (undoing steps 3-5); it
-   leaves Python alone, because there might be other applications using Python.
 
 The installer (and uninstaller) is produced using `NSIS
 <http://nsis.sourceforge.net/Main_Page>`_, with the Modern UI.