Make `trystan/silently` redirect to `hspec/silently`

[soenkehahn]

We (@sol and me) have moved silently to the hspec organization, taken over maintainership and made a release to hackage. If we can we would like to get a redirect from trystan/silently to hspec/silently (both on github) in place.

[sol]

@trystan Regarding the redirect, I think you would need to delete trystan/silently and then ping the GitHub support to set up the redirect to hspec/silently.