Clean logs on start - and eslint/mocha with code coverage (#1945)

* Clean logs on startup; install server-side testing/linting

* Add eslint config, make all of app/ conform to its demands

* Add Node.js testing and linting to CI

* Lock project to Node.js 7.9.0, used by Electron 1.7.10

* New eslint error: trailing commas in function argumensts

Node 7.9.0 doesn't like trailing commas, but Electron does

* Move electron to devDependency, tell eslint it's built-in

test/.eslintrc.js

@@ -0,0 +1,17 @@
+// For reference: https://github.com/airbnb/javascript
+
+module.exports = {
+  env: {
+    mocha: true,
+  },
+
+  rules: {
+    // We still get the value of this rule, it just allows for dev deps
+    'import/no-extraneous-dependencies': ['error', {
+      devDependencies: true
+    }],
+
+    // We want to keep each test structured the same, even if its contents are tiny
+    'arrow-body-style': 'off',
+  }
+};