@ashfurrow => Update formatter

NSDecimal seems to do some pretty inexact math, returning totally weird strings.
We were also doing some string manipulation to achieve the format we wanted when in fact we can set up the formatter itself to do what we want. I eliminated doing any actual math and added a method that accepts a dollar value, too, because I noticed in eidolon we were multiplying a dollar integer by 100 to feed to the `cents` method, which in turn spits back a dollar string.