build: use github mirror of bsaes dependency

This allows us to not depend on external hosts for third-party
dependencies other than the standard hosts: github.com,
google.golang.org, and gopkg.in.

go.mod

@@ -53,3 +53,5 @@ require (
 replace github.com/lightningnetwork/lnd/ticker => ./ticker
 
 replace github.com/lightningnetwork/lnd/queue => ./queue
+
+replace git.schwanenlied.me/yawning/bsaes.git => github.com/Yawning/bsaes v0.0.0-20180720073208-c0276d75487e