[CM] new cm-2.4.0 tarfile available/install help

[Tobias Kunze Briseño]

> scripts looks for 'cm.tar.gz'

not really, it _looks_ for an image in a generic 'cm' directory
if you don't pass in a version option (so you can have a 'default'
version), and will also _build_ in this tree if necessary, but it 
won't _fetch_ a generic archive just yet (rick promised to maintain
a 'cm-newest' link on the ftp server once he's got a minute of free
time).