Making Pseudorandom compatible with Elm 0.13

Just added a few modifications to Pseudorandom.elm because of [breaking changes in Elm 0.13](https://github.com/elm-lang/elm-compiler/blob/master/changelog.md#breaking-changes-1):

> * Rename (.) to (<<) as in F#
> * Rename Basics.id to Basics.identity
> * Rename Basics.mod to (%)

Additionally, the Elm compiler now complains about if you try to import `Bitwise`'s `xor` into the main namespace (since it conflicts with `Basic.xor`), so I fully qualified the namespace for `Bitwise.xor`, `Bitwise.shiftLeft`, and `Bitwise.shiftRight`).