'numerator and 'denominator fail to handle integral values (i.e. N/1)

Because ratio values reduce to lowest terms and, for integral values where the lowest term is N/1, are auto-converted to BigInts (and formerly Longs), the current behavior of clojure.core/numerator and clojure.core/denominator yield unexpected results.

It's confusing to not support numerator and denominator on integer types as this requires you to always check ratio? before invoking them.

Proposed: Extend numerator and denominator to also work on integer types (long, BigInt, BigInteger) by routing to overloaded methods on Numbers for the desired types.

Patch: clj-1435.patch

Screened by: Alex Miller

Questions from screening for Rich:

1. numerator and denominator are tagged as returning java.math.BigInteger (not clojure.lang.BigInt) and that's what I followed in the patch. Seems like maybe that should be BigInt though? Not sure on what basis to make that decision.
2. Should numerator and denominator accept both BigInteger and BigInt?