Default to ~/Library/Caches/carthage/dependencies
Use the bundle identifier.
Merge remote-tracking branch 'origin/master' into caches
Add try() temporarily.

I can’t reasonably bump LlamaKit because Commandant and RAC can’t build
with its notion of ErrorType. So I’m bringing try() in manually.
Add `Result.either`.

Let’s not kid ourselves, this thing is `Either` in different guise.
Extract the bundle identifier into a global.
Extract the caches URL into a global.
Handle caches lookup failures by falling back to the old URL.

~/.carthage/dependencies lives on.
Extract the fallback URL into a global.
Merge remote-tracking branch 'origin/master' into caches
Merge remote-tracking branch 'origin/master' into caches
Just die a lonely death if there is no caches dir.
Some docs.
Make a best effort attempt to clean up old deps.
Remove ~/.carthage, not just its subdirectory.
Rename the caches URL global.
Export the bundle identifier string.
try(), try() again.
either(), either() again.
Spit out a warning if all does not go as planned.