vendor: update all dependencies

* Update all dependencies
  * Remove all `[[constraint]]` from Gopkg.toml
  * Add in the minimum number of `[[override]]` to build
  * Remove go get of github.com/inconshreveable/mousetrap as it is vendored
  * Update docs with new policy on constraints

vendor/golang.org/x/crypto/scrypt/scrypt.go

@@ -218,7 +218,7 @@ func smix(b []byte, r, N int, v, xy []uint32) {
 // For example, you can get a derived key for e.g. AES-256 (which needs a
 // 32-byte key) by doing:
 //
-//      dk, err := scrypt.Key([]byte("some password"), salt, 16384, 8, 1, 32)
+//      dk, err := scrypt.Key([]byte("some password"), salt, 32768, 8, 1, 32)
 //
 // The recommended parameters for interactive logins as of 2017 are N=32768, r=8
 // and p=1. The parameters N, r, and p should be increased as memory latency and