fix(package): update tree-kill to version 1.2.1

Author: greenkeeper[bot]

package.json

@@ -66,7 +66,7 @@
     "relay-runtime": "1.6.0",
     "temp": "0.8.3",
     "tinycolor2": "1.4.1",
-    "tree-kill": "1.2.0",
+    "tree-kill": "1.2.1",
     "underscore-plus": "1.6.8",
     "what-the-diff": "0.4.0",
     "what-the-status": "1.0.3",