- added a generator that yields all files under all directories in the PATH environment variable for the purposes of determining whether or not virtualenv/pipsi are already installed
 - made all path specifiers portable by using os.path.join
 - wrote batchfile-wrapper generating routine so this will run on Windows where os.symlink does not work, either because of an old version of Python being employed, symlinks not existing, or the user not having permission to create symlinks
 - changed out all '\n' for os.linesep for portability
- moved Popen import to the top of the file
 - added symlink wrapper method to add the ability to create wrapper batchfiles where appropriate like in get-pipsi.py
 - abstracted platform-specific path stuff
 - added an inner method to real_readlink to read the source file out of a wrapper batchfile and return that as though the batchfile were actually a symlink
 - rewrote the important part of Repo.find_scripts to use pkg_resources.find_distributions instead of calling another Python within Popen