crypto: switch to golang.org/x/crypto

Godeps/Godeps.json

...orkspace/src/code.google.com/p/go.crypto/pbkdf2/pbkdf2.go

...ace/src/code.google.com/p/go.crypto/pbkdf2/pbkdf2_test.go

..._workspace/src/golang.org/x/crypto/ripemd160/ripemd160.go

...space/src/golang.org/x/crypto/ripemd160/ripemd160_test.go

...space/src/golang.org/x/crypto/ripemd160/ripemd160block.go

Godeps/_workspace/src/golang.org/x/crypto/scrypt/scrypt.go

.../_workspace/src/golang.org/x/crypto/scrypt/scrypt_test.go

crypto/crypto.go

crypto/key_store_passphrase.go