Use absolute import for OCCViewer; fix an inheritance issue

This fixes issue #25
Merge pull request #27 from tpaviot/review/py3k-fixes

py3k fixes
importing a module ( file ) from the same directory is only possible with the relative import syntax
however, I prefer the more consistent "from OCC.Display import X" syntax

finally, `apply` is no longer a keyword in py3k, so that's updated to unpacking the arguments form a tuple
Added draft for sphinx doc for examples
Added sphinx autogenerated API documentation
Added README