Lock electron-mksnapshot to the version used in Atom

Author: smashwilson

package-lock.json

@@ -84,7 +84,7 @@
     "dedent-js": "1.0.1",
     "electron-devtools-installer": "2.2.4",
     "electron-link": "0.3.2",
-    "electron-mksnapshot": "3.0.0-beta.1",
+    "electron-mksnapshot": "~2.0",
     "enzyme": "3.8.0",
     "enzyme-adapter-react-16": "1.7.1",
     "eslint": "5.0.1",