message: chore(core): lock openpgp version
  lock at 5.1.0
  Ticket:
diff: "eosjs-ecc": "^4.0.4",
  "lodash": "^4.17.14",
  "moment": "^2.20.1",
  - "openpgp": "^5.1.0",
  + "openpgp": "5.1.0",
  "ripple-address-codec": "~4.1.3",
  "ripple-binary-codec": "~0.2.4",
  "ripple-keypairs": "^0.11.0",
  