Add support for response wrapping #78

[dubreuia]

See issue https://github.com/BetterCloud/vault-java-driver/issues/78

[dubreuia]

Added response wrapping token lookup for validation purpose https://www.vaultproject.io/docs/concepts/response-wrapping.html#response-wrapping-token-validation, typically adding the call to "sys/wrapping/lookup" from https://www.vaultproject.io/docs/concepts/response-wrapping.html#response-wrapping-token-operations

[steve-perkins]

Thanks so much!