chore(package): update gulp-conventional-changelog to version 2.0.15

Author: greenkeeper[bot]

package.json

@@ -50,7 +50,7 @@
     "gulp": "4.0.1",
     "gulp-babel": "8.0.0",
     "gulp-bump": "3.1.3",
-    "gulp-conventional-changelog": "2.0.10",
+    "gulp-conventional-changelog": "2.0.15",
     "gulp-eslint": "5.0.0",
     "gulp-git": "2.9.0",
     "gulp-jasmine": "4.0.0",