Infinitely expandable get_distinct and get_number functions, and graphing!

Graphing requires matplotlib, I installed Anaconda to get it.

get_distinct and get_number now accept any number of parameters, and
will restrict the data set further for every column name and column
label added.

Example: To get all the possible converted mana costs in black, you
would call:
cube.get_distinct('CMC', 'Color', 'MONO_BLACK')
To get all the possible CMCs of creatures in black, you would call:
cube.get_distinct('CMC, 'Color', 'MONO_BLACK', 'Card_Type', 'CREATURE')