Added MKFoundationKit/NSNumber dependency.
Updated specs.
Replaced Fraction category with MKFoundationKit/NSNumber.
Replaced Negative category with MKFoundationKit/NSNumber.
Removed legacy files.
Removed category tests.
Restructured files.
Renamed category to +Quantity
Added NSNumber category for simplicity.
.
Extended MassImperial with NSNumber category.
Extended LengthUnits with NSNumber category.
Extended AreaUnits with NSNumber category.
Extended ByteUnits with NSNumber category.
.
Extended TimeUnits with NSNumber category.
Updated README.
Added Example.
Updated README.md
Added comments.