chore(package): update proxyquire to version 2.1.0

Closes #32

Author: greenkeeper[bot]

package.json

@@ -33,7 +33,7 @@
     "errno-codes": "^1.0.2",
     "istanbul": "^0.4.5",
     "mocha": "^3.0.2",
-    "proxyquire": "^1.7.10",
+    "proxyquire": "^2.1.0",
     "rimraf": "^2.5.4",
     "sinon": "^1.17.6",
     "sinon-chai": "^2.8.0"