message: use crypto randomBytes instead of math.random
diff: +import { randomBytes } from 'crypto'
  +
  /* @flow */
  export const BLOCKSTACK_HANDLER = 'blockstack'
  /**
  @@ -55,7 +57,7 @@ export function makeUUID4() {
  d += performance.now() // use high-precision timer if available
  }
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, (c) => {
  - const r = (d + Math.random() * 16) % 16 | 0
  + const r = (d + (randomBytes(1).readUInt8() % 16)) % 16
  d = Math.floor(d / 16)
  return (c === 'x' ? r : (r & 0x3 | 0x8)).toString(16)
  })
  