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

.eslintrc.js

@@ -0,0 +1,41 @@
+// For reference: https://github.com/airbnb/javascript
+
+module.exports = {
+  settings: {
+    'import/core-modules': [
+      'electron'
+    ]
+  },
+
+  extends: [
+    'airbnb-base',
+  ],
+
+  rules: {
+    'comma-dangle': ['error', {
+        arrays: 'always-multiline',
+        objects: 'always-multiline',
+        imports: 'always-multiline',
+        exports: 'always-multiline',
+        functions: 'never',
+    }],
+
+    // putting params on their own line helps stay within line length limit
+    'function-paren-newline': ['error', 'consistent'],
+
+    // 90 characters allows three+ side-by-side screens on a standard-size monitor
+    'max-len': ['error', {
+      code: 90,
+      ignoreUrls: true,
+    }],
+
+    // it helps readability to put public API at top,
+    'no-use-before-define': 'off',
+
+    // useful for unused or internal fields
+    'no-underscore-dangle': 'off',
+
+    // though we have a logger, we still remap console to log to disk
+    'no-console': 'off',
+  }
+};