Installation issues with virtual-node and virtual-less

Currently there are some issues with creating the sandbox due to the way ``setuptools`` installs packages when using the ``develop`` command. I opened a new issue for to avoid confusion with haystack related issues in #522 and #384. These issues are related but I'd rather deal with this issue separately. 

I have looked at this and there's no easy solution for this. It might be compile node into the environment using the extension installation process of ``setuptools`` and make it a "fake" extension. This would work more along the lines of PIL but is total speculation at this point. I have to check it out as soon as I get time. 

Until then I'd like to propose a solution that might be advantageous in an additional way. Since not everybody might want to have an installation of node and less in their virtualenv, especially when a global installation of both already exists, it might make more sense to have a ``requirements_compressor.txt`` script rather than a dependency in ``setup.py`` and add the corresponding bit of documentation. 
@codeinthehole, @maikhoepfel: What are your thoughts on this?