run4.py is the working version

run it as follows:

python run4.py s1-exa2-solution.ipynb test2.py user/home/dir to see a succesful file

and the following to see the output on a skeleton file, which will fail:

python run4.py s1-exa2-challenge.ipynb test2.py user/home/dir

The system output from the script is -1 if any test fails, or 0 if all tests pass.Also it outputs JSON as response.This JSON is consumed by assessor forked from this Repo