depended on were installed too.  This is nice under normal
circumstances, but when the install command is used with a list of
parts, then the promise is that *only* those parts will be installed.
This is an important use case, because it can speed development.


git-svn-id: http://svn.zope.org/repos/main/zc.buildout/trunk@71477 62d5b8a3-27da-0310-9561-8e5933582275