Matlab error messages on run_code hard to debug #239

This is a fix that would greatly improve things like matlab_kernel. Could we (maybe only when requested by a flag) pass the matlab code to be executed to matlab in a line-by-line fashion? That way, if you have a 30 line script in a Jupyter notebook cell and you get back an "Index exceeds matrix dimensions" error, you can check which line caused the error?

As it stands, the fastest way to debug this kind of thing is to bisect the script by manually commenting out chunks of it at a time, which is pretty miserable. I could easily implement this if you like the idea but have no time.

To reproduce bug:

m = Matlab()
m.start()
m.run_code("""
a = 3;
% many lines of code
a(2);
% many more lines of code
""")