added fetching of current pricelists from tcgplayer

this is a python 3 version of your code, I've added the ability to pull your csv price lists directly from tcgplayer.

example:
python3 calc-ev.py Modern Masters
     >>> Foils Pulled: 36 at an average price of $7.54
     >>> Mythics Pulled: 27 at an average price of $28.90
     >>> Rares Pulled: 189 at an average price of $5.07
     >>> Bulk Uncommon/Common Play Sets: 2.55 at an average price of $25.00
     >>> Total Box Estimated Value: $345.49