Update diceRoller.py

The changes I made:
Changed the top comment to relate to the program.
Fixed the import errors.
Adjusted the functions to work correctly with each other.
Added functionality so when a six is rolled the user wins.
Made the whole program more efficient by using a list to contain the dice faces, and a single line of code to deal with the generated number and output the dice face.

My version of the code for 23rd May.