Set globals to {}

[pavelzw]

Fixes #3

When you don't set the globals in exec, they get inherited from the point where exec is called. Then, pd won't get added to the globals while running the method.

Debugging pythonji with globals set:

pythonji-with-globals.mov

Debugging pythonji without setting globals:

pythonji-no-globals.mp4

[pavelzw]

Added to pavelzw/pythonji-2 since this is apparently not maintained anymore.