A la carte syntax for Spire.

This is a major refactor of Spire's syntax/operator support. It now
follows a Scalaz style importable syntax per typeclass.

Note that a blanket import of spire.implicits._ will still give you all
the syntax as before.

Example use of new imports:

Get access to +, -, *, **, etc.

    import spire.syntax.ring._ 

Get access to <, >, <=, ===, etc.

    import spire.syntax.order._

Get access to /~, **, etc for Int.

    import spire.syntax.std.int._

Get access to Rational literals and the like.

    import spire.syntax.literals._

Get cfor.

    import spire.syntax.cfor._