Switch setup.py to setuptools

Add install_requires so that setuptools does smart dependency management, and use a try-except fallback if the user doesn't have setuptools installed.

Use try-except fallback for setuptools/distutils
Merge pull request #40 from bjlange/fix-setup

add setuptools as preferred library for setup.py
add tox.ini
convert README to restructuredText (.rst)
add Makefile target to generate README.html
update mailing list to googlegroups in README.rst
Extend picture() and savedocx() to save pictures without copying them to
the template directory. When the same image file is used multiple times,
no duplicates will be added.

Caveat: to prevent image files from accumulating in word/media/ across
runs, never call picture() and savedocx() without the imagefiledict
parameter. The imagefiledict is optional because of backward compatibility.