Remove buildout.

> Actually this is meant to handle both virtualenvwrapper and virtualenv.

In the past, I used buildout to make sure every developer setup the same environment. But I came to the conclusion Python environment setup is really a matter of preferences. Explaining the reasons, explaining how to, and maintaining environment setup requires time and efforts.
I'd prefer say "transmutator's Makefile needs Python x.x.", suggest "Use virtualenv if you like." but actually let the developer choose the tool he is confident with.
Then from our point of view, provided we can use or install tox, we are ok.

> Some people are not developers and should not bother about virtualenv or virtualenvwrapper.

The Makefile is made for development purpose (if you do not want to develop transmutator, just install it with `pip install transmutator`). Since transmutator is written in Python, I think the Python environment setup is a basic operation for developers.
And because some people do not want to bother with virtualenv or virtualenvwrapper,  let's allow them do what they like ;)