Update globby to version 8.0.0 (postcss#197)

Author: greenkeeper[bot]

package.json

@@ -23,7 +23,7 @@
     "dependency-graph": "^0.7.0",
     "fs-extra": "^5.0.0",
     "get-stdin": "^5.0.1",
-    "globby": "^7.1.1",
+    "globby": "^8.0.0",
     "postcss": "^6.0.1",
     "postcss-load-config": "^1.1.0",
     "postcss-reporter": "^5.0.0",