chore(package): update proxyquire to version 2.0.0

Author: greenkeeper[bot]

package.json

@@ -49,7 +49,7 @@
     "postcss-mixins": "^6.0.1",
     "postcss-scss": "^1.0.2",
     "postcss-simple-vars": "^4.0.0",
-    "proxyquire": "^1.8.0",
+    "proxyquire": "^2.0.0",
     "rimraf": "^2.6.1",
     "semantic-release": "^12.0.0",
     "sinon": "^4.0.0",