fix(package): update which to version 2.0.1

Closes #132

Author: greenkeeper[bot]

package.json

@@ -32,7 +32,7 @@
   "dependencies": {
     "cross-spawn": "^5.0.1",
     "spawn-sync": "^1.0.15",
-    "which": "1.2.x"
+    "which": "~2.0.1"
   },
   "devDependencies": {
     "assume": "~1.5.0",