Special treatment for NaN and Infinity as per RFC-4627.

> Numeric values that cannot be represented as sequences of digits
> (such as Infinity and NaN) are not permitted.

http://tools.ietf.org/html/rfc4627#page-3
Merge branch 'master' of https://github.com/folone/argonaut into folone-master
Follow up to #58.

Make sure the changes to jNumber result in a compile
error.

Add combinators to give options for lossless and
optional constructions.

Update tests.