ProgressBar() module to display output to a console or iPython Re: issue#2658

Modified ProgressBar() module to display output to a console or iPython notebook, depending on additional 'interactive' kwarg.

Description of the issue and possible fix here: http://nbviewer.ipython.org/gist/astrocaribe/398d04434430c3f44617

Receiving an AttributeError on this line if value = None. Does this mean that ._current_value does not exist until value passed to either _update_console() or _update_interactive()?