python 3.3 import errors #28

When trying to install from the mercurial tip (changeset 36:3c94a3a1ebe1 from 
September 21), I get the following error:

     Traceback (most recent call last):
      File "setup.py", line 5, in <module>
        import progressbar
      File "/usr/local/src/python-progressbar/progressbar/__init__.py", line 47, in <module>
        from compat import *
    ImportError: No module named 'compat'

This is because the imports aren't relative to the current package. Changing 
the imports in __init__.py to 

     from .compat import *

and so on works, as would `from progressbar.compat`.

I also needed to change `import widgets` to `from . import widgets` in 
`progressbar.py`. Then everything worked.

Also note that the version in pypi (2.3-dev) still has the `__slots__` problem 
that was fixed back in September - it'd be nice to release a new version with 
these two problems fixed, so `pip install progressbar` works.