message: Seperated error handling
diff: @@ -158,15 +158,16 @@ class AlexaInteractionModel {
  _.set(alexaModel, 'interactionModel.languageModel.invocationName', model.invocation);
  // handle invocation name requirements
  - if (alexaModel.interactionModel.languageModel.invocationName.length === 0) {
  - throw new Error(errorPrefix + 'Invocation cannot be empty');
  - }
  if (alexaModel.interactionModel.languageModel.invocationName.length < 2 ||
  alexaModel.interactionModel.languageModel.invocationName.length > 50) {
  throw new Error(errorPrefix + 'Invocation name must be between 2 and 50 characters.');
  }
  - if(/[A-Z0-9\d]/.test(alexaModel.interactionModel.languageModel.invocationName)){
  + if(/[A-Z]/.test(alexaModel.interactionModel.languageModel.invocationName)){
  + throw new Error(errorPrefix + 'Invocation name cannot contain upper case characters.');
  + }
  +
  + if(/\d/.test(alexaModel.interactionModel.languageModel.invocationName)){
  throw new Error(errorPrefix + 'Invocation name may only contain alphabetic characters, apostrophes, periods and spaces.');
  }
  