Feat/fix binding demo pipeline

[LimHyungTae]

I checked bindings_demo.py does not work now.

So I'd like to do this PR to address that issue.

[nathanhhughes]

The issue that you're having is that you're visualizing a scene graph with 2D places ('P' is the prefix for 2D places, 'p' is the prefix for 3D places). I'm not opposed to the fix, but I'd rather solve it by providing defaults for unknown prefixes (i.e., by doing something like MARKER_SIZES.get(prefix, 6) (or whatever the actual offending dictionary was called).

I'll add an actual review once this gets rebased on develop (sorry, had a backlog of issues / PRs to work through and needed to update the history for develop)

Closes #24