Fixing combineURLs to support an empty relativeURL

When combining the base and relative URLs, we should forego force
appending a slash to the base when the relative URL is empty.
This leads to a semantic url.

lib/helpers/combineURLs.js

@@ -8,5 +8,8 @@
  * @returns {string} The combined URL
  */
 module.exports = function combineURLs(baseURL, relativeURL) {
-  return baseURL.replace(/\/+$/, '') + '/' + relativeURL.replace(/^\/+/, '');
+  var end = relativeURL.replace(/^\/+/, '');
+  return end
+    ? baseURL.replace(/\/+$/, '') + '/' + end
+    : baseURL;
 };

test/specs/helpers/combineURLs.spec.js

@@ -12,4 +12,8 @@ describe('helpers::combineURLs', function () {
   it('should insert missing slash', function () {
     expect(combineURLs('https://api.github.com', 'users')).toBe('https://api.github.com/users');
   });
+
+  it('should not insert slash when relative url missing/empty', function () {
+    expect(combineURLs('https://api.github.com/users', '')).toBe('https://api.github.com/users');
+  });
 });