Upgrade electron-devtools-installer.

Fixes
https://github.com/MarshallOfSound/electron-devtools-installer/pull/64
& https://github.com/LN-Zap/zap-desktop/issues/78.

package.json

@@ -143,7 +143,7 @@
     "css-loader": "^0.28.3",
     "electron": "^1.6.10",
     "electron-builder": "^19.8.0",
-    "electron-devtools-installer": "^2.2.0",
+    "electron-devtools-installer": "^2.2.1",
     "enzyme": "^2.9.1",
     "enzyme-to-json": "^1.5.1",
     "eslint": "^4.4.1",

yarn.lock

@@ -2923,9 +2923,9 @@ electron-debug@^1.2.0:
     electron-is-dev "^0.1.0"
     electron-localshortcut "^2.0.0"
 
-electron-devtools-installer@^2.2.0:
-  version "2.2.0"
-  resolved "https://registry.yarnpkg.com/electron-devtools-installer/-/electron-devtools-installer-2.2.0.tgz#9813e6811afcd69ddca3cae5416db72ea7ecfb6a"
+electron-devtools-installer@^2.2.1:
+  version "2.2.1"
+  resolved "https://registry.yarnpkg.com/electron-devtools-installer/-/electron-devtools-installer-2.2.1.tgz#0beb73ccbf65cbc4d09e706cebda638f839b8c55"
   dependencies:
     "7zip" "0.0.6"
     cross-unzip "0.0.2"