Converted Double-Tabs to Spaces

Converted double tabs to 4 spaces.

Per the [PEP8 standard](http://www.python.org/dev/peps/pep-0008/#tabs-or-spaces), spaces are preferred to tabs.

The way it was before, lines seemed to be indented with double tabs - this makes it incredibly difficult to develop in most environments, and is generally just ugly. I'm not sure what your development environment looks like, however, it should be trivial to switch the editor to using spaces. This should make things more consistent, as well as hopefully make it easier for contributors to work with.

Also just changed except Exception to except ImportError for importing packages.