Allow formatter combos

I put the code for the two existing formatters into modules in order to allow multiple inheritance.  For organization, they're set up as submodules of NyanCatFormat.  Each "formatter" class simply includes the related module and they function as expected.

Now you can create combinations of multiple formatters by simply including the desired format modules in a new formatter class.  I created one that combines 'wide' and 'music'.  Yay.