Update documentation for new split, fixes haskell-hvr#8.

Policy.md

@@ -0,0 +1,11 @@
+# Versioning
+
+Because many consumers of the `UUID` type receive the type
+through the `uuid` package and not the `uuid-types` package
+we need to be careful about removing instances from the `uuid`
+type.
+
+If the `uuid-types` package has a major-version bump because of
+the removal of a class instance then we must also bump the major
+version of the `uuid` package when we update the package
+description to pull in the new version of `uuid-types`.

README.md

@@ -2,3 +2,11 @@
 
 This library is useful for creating, comparing, parsing and printing Universally
 Unique Identifiers. See http://en.wikipedia.org/wiki/UUID for the general idea.
+
+We offer two different packages: `uuid` and `uuid-types`
+
+The `uuid` package aims to be a fully-featured library for working with UUIDs.
+
+However if you're developing a library and only want the `UUID` type to show up
+in your APIs you may want to use the `uuid-types` library to minimize the number
+of dependencies needed by users of your library.