Fixed indentation for base classes and twitter-mod.

Seeing how 80% of the project was space-indentation and the rest based on tabs, I went ahead and converted the base classes and twitter-mod to space-only indentation (and fixed a few indentation mishaps on the way). Whatever we decide to prefer (spaces or tabs), this lets us easily convert to it. In the end, personally I don't care. Just pick one and stick to it :-)