Intermediate commit. I was working on some edits and then... stopped for some reason.
Updated the cogal_demo function to be cleaner and better.

Minor things mainly. No longer do we generate a viewer in the function itself. The user can do that.
Implemented the save & load functions for dendrograms.

In the end they are useless because dendrograms loaded from disk don't have the right interconnectivity. Their structure branch things don't have defined self._dendrograms! and that's needed for some stuff.
Updated .gitignore to ignore a lot of dudes.