chore(package): update sinon to version 6.0.0

Closes #97

Author: greenkeeper[bot]

package.json

@@ -26,7 +26,7 @@
     "istanbul": "^0.4.5",
     "mocha": "^5.0.0",
     "pre-commit": "^1.2.2",
-    "sinon": "^4.0.0",
+    "sinon": "^6.0.0",
     "sinon-chai": "^2.8.0"
   },
   "repository": "git@github.com:Moveo/minimize.git",