Add scala.math type class wrappers.
Add scala.math type class wrappers.

This adds wrappers for Scala's Ordering, Equiv, Numeric, Integral, and
Fractional that use Spire's type classes underneath. This is purely for
better interop with the Scala standard library and other 3rd party
libraries that use Scala's boxing type classes.

adampingel/spire,siddhartha-gadgil/spire,kevinmeredith/spire,woparry/spire,siddhartha-gadgil/spire,tixxit/spire,guersam/spire,adampingel/spire,JackSullivan/spire,woparry/spire,non/spire,JackSullivan/spire,guersam/spire,non/spire,tixxit/spire,AlecZorab/spire,kevinmeredith/spire,codeaudit/spire,rklaehn/spire,rklaehn/spire,AlecZorab/spire,codeaudit/spire