code: function checkAddressBalance(url, address, options) {
    options = options || {};
    let path = '/address/.../balance'.replace('...', address);
    url = resolveURL(url, path);
  
    return new P(function (resolve, reject) {
      request({
        url: url,
        method: 'GET',
        headers: options.headers
      }, function (err, res, body) {
        if (err) return reject(err);
        return resolve(body);
      });
    });
  }
docs: Checks the balance of a wallet address
  @param {string} url - The URL of a webwallet server
  @param {string} address - A wallet address
  @param {Object} options - Request parameters such as headers
  @return {Promise} - Resolves to the response body