Update get-stdin to version 7.0.0 (#273)

Author: greenkeeper[bot]

package.json

@@ -22,7 +22,7 @@
     "chokidar": "^2.0.0",
     "dependency-graph": "^0.8.0",
     "fs-extra": "^7.0.0",
-    "get-stdin": "^6.0.0",
+    "get-stdin": "^7.0.0",
     "globby": "^9.0.0",
     "postcss": "^7.0.0",
     "postcss-load-config": "^2.0.0",