hyperdeck.format fix context scoping

[TomKaltz]

this inside a then was not scoped correctly.

[tjenkinson]

hey @TomKaltz thanks for the PR!

Please could you change it to

  this.format = function(format){
    return this.makeRequest('format: prepare: ' + format).then(function(response) {
      if (response.code !== 216 || response.text !== 'format ready' || !response.rawData) {
        throw new Error('Unexpected response.');
      }
      var token = response.rawData;
      return this.makeRequest('format: confirm: ' + token);
    }.bind(this));
  };

instead? We don't support es6 anywhere else in the code.

[tjenkinson]

thanks published as 1.4.1