Req changes from code review

Author: LuisTejedaS

lib/schemaUtils.js

@@ -2125,7 +2125,7 @@ module.exports = {
     previewLanguage = this.resolveResponsePreviewLanguageAndResponseHeader(responseBodyWrapper,
       responseHeaders, response);
     // replace 'X' char with '0'
-    code = code.replace(/X/g, '0');
+    code = code.replace(/X|x/g, '0');
     code = code === 'default' ? 500 : _.toSafeInteger(code);
 
     sdkResponse = new sdk.Response({
@@ -2140,6 +2140,13 @@ module.exports = {
     return sdkResponse;
   },
 
+  /**
+   * Identifies the previewLanguage to use and also adds the identified content header to the responseHeaders array
+   * @param {object} responseBodyWrapper generated response body and its related information
+   * @param {object} responseHeaders - The existent array of response headers
+   * @param {object} response in operationItem responses
+   * @returns {string} previewLanguage
+   */
   resolveResponsePreviewLanguageAndResponseHeader: function (responseBodyWrapper,
     responseHeaders, response) {
     let previewLanguage = 'text';

test/unit/x20schemapack.test.js

@@ -76,6 +76,9 @@ describe('Convert method', function() {
       expect(error).to.be.null;
       expect(result.output[0].data.item[0].response[0]._postman_previewlanguage).to.equal('json');
       expect(result.output[0].data.item[0].response[0].body).to.not.be.empty;
+      expect(result.output[0].data.item[0].response[0].header.find((header) => {
+        return header.key === 'Content-Type';
+      }).value).to.equal('*/*');
     });
     done();
   });