py3.3 doesn't download distribute correctly, fails build

I have a vague memory of seeing this issue come up before, but I can't seem to find it now, so I'm making a new one - If it's a dup, sorry, and this can be closed.

For 0.3 we definitely want python 3.3 to be fully supported (by then, scipy should also support it).  Right now, though, if I try to do ``python3.3 setup.py build``, without a system install of distribute (at least, I don't *think* there is one...), I get the following traceback:
```
Freezing version number to astropy/version.py
Traceback (most recent call last):
  File "setup.py", line 82, in <module>
    package_dirs)
  File "/Users/erik/src/astropy/astropy/setup_helpers.py", line 961, in update_package_files
    extensions.extend(setuppkg.get_extensions())
  File "astropy/wcs/setup_package.py", line 204, in get_extensions
    from astropy.version import debug
ImportError: No module named 'astropy.version'
```

If I get it to pull down the latest distribute, though, it works fine.  It's also possible this is a distribute *versioning* problem, because it doesn't seem to be completely reproducible (although I admit I'm not being terribly careful, so I recommend someone else cross-check that part) 

@iguananaut @astrofrog