Update postcss-reporter to version 6.0.0 (#238)

Author: greenkeeper[bot]

package.json

@@ -26,7 +26,7 @@
     "globby": "^8.0.0",
     "postcss": "^7.0.0",
     "postcss-load-config": "^2.0.0",
-    "postcss-reporter": "^5.0.0",
+    "postcss-reporter": "^6.0.0",
     "pretty-hrtime": "^1.0.3",
     "read-cache": "^1.0.0",
     "yargs": "^12.0.1"