Add ipython support to ./bin/gmg shell

[Christopher Allan Webber]

It would be great if we could launch ipython optionally like:

  ./bin/gmg shell --ipython

There's some code in werkzeug's codebase that looks like it does this the right way.

        if ipython:
            try:
                try:
                    from IPython.frontend.terminal.embed import InteractiveShellEmbed
                    sh = InteractiveShellEmbed(banner1=banner)
                except ImportError:
                    from IPython.Shell import IPShellEmbed
                    sh = IPShellEmbed(banner=banner)
            except ImportError:
                pass
            else:
                sh(global_ns={}, local_ns=namespace)
                return
        from code import interact
        interact(banner, local=namespace)

If we borrow a significant chunk of this code, we should annotate correctly:

​http://www.softwarefreedom.org/resources/2007/gpl-non-gpl-collaboration.html

[Christopher Allan Webber]

This is merged actually! Thanks Hugo!