Support --dry-run option.

Switched to using ``distutils.dir_util`` instead of ``shutil`` to
remove directories since it has nice support for dry run already.
Support defaulted parameters to other commands.

Switched from enumerating ``self.distribution.commands`` to using
``self.distribution.get_command_list``.  The former is the list of
command names that will be run and the latter is the list of all
known commands.  This will make the code work when you do not
include something like ``sdist`` in the same command list.
Support removal of .egg and .egg-info directories.
Verify that `--dry-run` works with `--eggs`.
tests: Simply assert_path... methods.
Correct image paths & links in README.
setup.py: Enable extended clean command.

Might as well make use of the extension here as well.  This makes it
much easier to test some of the trickier stuff like setting the egg
base directory via the egg_info command in the setup configuration
file.
Bumps for 0.0.2 release.
Merge pull request #2 from dave-shawley/add-egg-support

Add egg support