Implement traits from the rand crate.

[lemmih]

It would be nice to have these implementations behind an optional dependency on rand. Would you accept a PR?

impl<T> Distribution<NonNan<T>> for Standard {}
impl<T> Distribution<NonNan<T>> for Open01 {}
impl<T> Distribution<NonNan<T>> for OpenClosed01 {}
impl<T> Distribution<OrderedFloat<T>> for Standard {}
impl<T> Distribution<OrderedFloat<T>> for Open01 {}
impl<T> Distribution<OrderedFloat<T>> for OpenClosed01 {}

[mbrubeck]

Yes, a PR would be welcome.

[mbrubeck]

Fixed by #84.