code: function verifyHash(correctHash, filepath) {
      return calculateHash(filepath).then(hash => {
          if (hash !== correctHash) {
              throw new Error(`Incorrect checksum: expected ${correctHash}, got ${hash}`);
          }
          return true;
      });
  }
docs: Calculates SHA512 hash of filepath and compares
  it to the provided correctHash.
  
  Returns a promise which rejects if the hash is
  incorrect, otherwise resolves to true.
  
  @param {string} correctHash expected hex-encoded SHA-512 hash
  @param {string} filepath file path
  @returns {Promise<boolean>}