[wip] Lint the javascript code with eslint

```gulp lint```

Author: fredj

.eslintrc

@@ -0,0 +1,14 @@
+{
+  "extends": "eslint:recommended",
+  "env": {
+    "browser": true
+  },
+  "plugins": [
+    "html"
+  ],
+  "globals": {
+    "CustomElements": true,
+    "HTMLImports": true,
+    "Polymer": true
+  }
+}

gulpfile.js

@@ -20,6 +20,7 @@ var runseq = require('run-sequence');
 var lazypipe = require('lazypipe');
 var polyclean = require('polyclean');
 var del = require('del');
+var eslint = require('gulp-eslint');
 
 var path = require('path');
 
@@ -122,3 +123,9 @@ gulp.task('audit', function() {
 gulp.task('release', function(cb) {
   runseq('default', ['copy-bower-json', 'audit'], cb);
 });
+
+gulp.task('lint', function() {
+  return gulp.src('src/**/*.html')
+    .pipe(eslint())
+    .pipe(eslint.format());
+});

package.json

@@ -9,8 +9,10 @@
   },
   "devDependencies": {
     "del": "^1.1.1",
+    "eslint-plugin-html": "^1.0.4",
     "gulp": "^3.8.11",
     "gulp-audit": "^1.0.0",
+    "gulp-eslint": "^1.0.0",
     "gulp-rename": "^1.2.2",
     "gulp-replace": "^0.5.3",
     "gulp-vulcanize": "^6.0.1",