Merge pull request #69 from jwien001/master

Finished work on adding a class.
Merge pull request #70 from jwien001/master

Further work on classes.
Merge pull request #71 from jwien001/master

Implemented deleting Problems.
Merge pull request #72 from jwien001/master

Implemented deleting Problem Sets.
Merge pull request #73 from jwien001/master

Deleting classes and a couple of bug fixes.
Merge pull request #74 from jwien001/master

Students can no longer add a Problem to a Set when creating a problem.
Added several PyInterpret features

Time limit to code runtime, recursion depth protection, and professor
code handling