Completely re-wrote R2Up method to be much simpler. Seems to have eliminated the errors involving this method.

Added test cases and a function called testR3 to the TestR3.py file.

Added test cases to TestR1.py file.

Simplified the TestR2Up.py file.

Added commas to the output of the to_list() method of an ADT object, for easier documentation of prolem-cases.