Synthesize method does not honor access_token from IAM API Key

[jeancarl]

In SDK v.0.36 with Firefox 60.3.0esr (64-bit), using the new IAM API Key authentication for Text to Speech, the synthesize method filters out the access_token parameter.

var params = {
  text: "Hello",
  voice: "en-US_MichaelVoice",
  access_token: "<ACCESS_TOKEN>"
};

stream = WatsonSpeech.TextToSpeech.synthesize(params);

The requested URI resource doesn't include this access token and the watson-token parameter is undefined, returning a CORS error.

https://stream.watsonplatform.net/text-to-speech/api/v1/synthesize?voice=en-US_MichaelVoice&text=Hello&watson-token=**undefined**

Fix

https://github.com/watson-developer-cloud/speech-javascript-sdk/blob/master/dist/watson-speech.js#L12127

Add access_token to the QUERY_PARAMS_ALLOWED array.

var QUERY_PARAMS_ALLOWED = ['voice', 'X-WDC-PL-OPT-OUT', 'X-Watson-Learning-Opt-Out', 'text', 'watson-token', 'accept', 'customization_id', 'access_token'];

There should also be a check that token parameter is defined, given it's either token or access_token.

module.exports = function synthesize(options) {
  if (!options || (!options.token && !options.access_token)) {
    throw new Error('Watson TextToSpeech: missing required parameter: options.token (CF) or options.access_token (RC)');
  }
  options['watson-token'] = options.token;
  delete options.token;
  var audio = options.element || new Audio();

Fix

module.exports = function synthesize(options) {
  if (!options || (!options.token && !options.access_token)) {
    throw new Error('Watson TextToSpeech: missing required parameter: options.token (CF) or options.access_token (RC)');
  }
  if(options.token) {
    options['watson-token'] = options.token;
    delete options.token;
  }
  var audio = options.element || new Audio();

[jeancarl]

Pull request #93 with changes.