Update and improve list headers in Dependencies.md

Dependencies.md

@@ -4,16 +4,16 @@ Dependencies
 [https://github.com/the-xkcd-community/the-red-spider-project]
 
 
-Strictly required for any use:
+Required for the setup script, `rsshell` and several commands:
 
 - [Python 2.7](http://www.python.org/download/) (unixy systems should have a `python2` link).
 
-Soon to be required for default installation:
+Required for the `level_up` command:
 
 - [Python 3](http://www.python.org/download/) (unixy systems will need to have a `python3` link, on Windows it will be convenient to have [pylauncher](https://bitbucket.org/vinay.sajip/pylauncher) installed);
 - [Tcl/Tk](http://www.tcl.tk/).
 
-Optional dependencies:
+Other dependencies:
 
 - Git, in order to participate (see [GitImmersion](http://gitimmersion.com/index.html) for installation and a tutorial);
 - [PHP](http://www.php.net/downloads.php) for [zed0/advbrowser](https://github.com/zed0/the-red-spider-project/tree/advbrowser);