Enforce a consistent ES6 coding style

Replace the old (and broken) jshint + jscsrc by eslint and configure
it to support some of the ES6 features.

The command `eslint` currently has one error which is a bug that was
discovered by its static analysis and should be fixed (usage of a
dead object).

client/config/router.js

@@ -6,7 +6,7 @@ FlowRouter.triggers.exit([({path}) => {
 FlowRouter.route('/', {
   name: 'home',
   triggersEnter: [AccountsTemplates.ensureSignedIn],
-  action: function() {
+  action() {
     Session.set('currentBoard', null);
     Session.set('currentCard', null);
 
@@ -14,14 +14,14 @@ FlowRouter.route('/', {
     EscapeActions.executeAll();
 
     BlazeLayout.render('defaultLayout', { content: 'boardList' });
-  }
+  },
 });
 
 FlowRouter.route('/b/:id/:slug', {
   name: 'board',
-  action: function(params) {
-    let currentBoard = params.id;
-    let previousBoard = Session.get('currentBoard');
+  action(params) {
+    const currentBoard = params.id;
+    const previousBoard = Session.get('currentBoard');
     Session.set('currentBoard', currentBoard);
     Session.set('currentCard', null);
 
@@ -32,57 +32,57 @@ FlowRouter.route('/b/:id/:slug', {
     }
 
     BlazeLayout.render('defaultLayout', { content: 'board' });
-  }
+  },
 });
 
 FlowRouter.route('/b/:boardId/:slug/:cardId', {
   name: 'card',
-  action: function(params) {
+  action(params) {
     Session.set('currentBoard', params.boardId);
     Session.set('currentCard', params.cardId);
 
     EscapeActions.executeUpTo('inlinedForm');
 
     BlazeLayout.render('defaultLayout', { content: 'board' });
-  }
+  },
 });
 
 FlowRouter.route('/shortcuts', {
   name: 'shortcuts',
-  action: function(params) {
+  action() {
     const shortcutsTemplate = 'keyboardShortcuts';
 
     EscapeActions.executeUpTo('popup-close');
 
     if (previousPath) {
       Modal.open(shortcutsTemplate, {
-        onCloseGoTo: previousPath
+        onCloseGoTo: previousPath,
       });
     } else {
       // XXX There is currently no way to escape this page on Sandstorm
       BlazeLayout.render('defaultLayout', { content: shortcutsTemplate });
     }
-  }
+  },
 });
 
 FlowRouter.notFound = {
-  action: function() {
+  action() {
     BlazeLayout.render('defaultLayout', { content: 'notFound' });
-  }
-}
+  },
+};
 
 // We maintain a list of redirections to ensure that we don't break old URLs
 // when we change our routing scheme.
-var redirections = {
+const redirections = {
   '/boards': '/',
   '/boards/:id/:slug': '/b/:id/:slug',
-  '/boards/:id/:slug/:cardId': '/b/:id/:slug/:cardId'
+  '/boards/:id/:slug/:cardId': '/b/:id/:slug/:cardId',
 };
 
-_.each(redirections, function(newPath, oldPath) {
+_.each(redirections, (newPath, oldPath) => {
   FlowRouter.route(oldPath, {
-    triggersEnter: [function(context, redirect) {
+    triggersEnter: [(context, redirect) => {
       redirect(FlowRouter.path(newPath, context.params));
-    }]
+    }],
   });
 });