Redirecting to the latest crate should only use non-yanked versions

[shepmaster]

Right now, if I visit https://crates.io/crates/quickcheck, I am redirected to the "This crate has been yanked" page (for version 0.4.2). However, we could just instead redirect to 0.4.1, the previous non-yanked version.

[Eh2406]

related to #76

[pnkfelix]

also related to (but distinct from) #145

[carols10cents]

This has been fixed by the changes in #592 !

[carols10cents]

Ok, this is not fixed completely. If I navigate to https://crates.io/crates/quickcheck directly, I correctly end up on the page for quickcheck 0.4.1.

HOWEVER if I search for quickcheck and click the search result link, I still end up with a page that says "this crate has been yanked" page that says 0.4.2 :( Something's not hooked up the way ember needs it to be :(