runipy/main.py: Handle the event of a `ShimWarning` being issued on iPython 4.x and properly import the needed items.
runipy/main.py: Handle the event of a `ShimWarning` being issued on iPython 4.x and properly import the needed items.

nanshe-org/runipy,DudLab/runipy,paulgb/runipy,jakirkham/runipy