- The easy_install module install and build functions now accept a
  versions argument that supplied to mapping from project name to
  version numbers.  This can be used to fix version numbers for
  required distributions and their depenencies.

When a version isn't fixed, using either a versions option or using
  a fixed version number in a requirement, then a debug log message is
  emitted indicating the version picked.  This is useful for setting
  versions options.

- Added a remove testing helper function that removes files or directories.


git-svn-id: http://svn.zope.org/repos/main/zc.buildout/trunk@73006 62d5b8a3-27da-0310-9561-8e5933582275