Update Ring

[lancecarlson]

Please update ring to the latest.

#96

@SergioBenitez @alexcrichton

[lholden]

Yeah... this is a bit of an issue as ring ends up having native code linked. When this happens, the rust compiler bails if you have another dep on a different version.

[SergioBenitez]

Done.

[Libbum]

This needs to happen again. (See briansmith/ring/issues/598, briansmith/ring/issues/607)

[SergioBenitez]

I'm fully aware, but there's no new stable release of ring, only an alpha. Furthermore, once briansmith/ring#619 lands, we can update ring without a new major release bump. I'll hold off until either one of these occurs.