add js linter

gulpfile.js

@@ -4,6 +4,7 @@ var rename = require('gulp-rename');
 var source = require('vinyl-source-stream');
 var sourcemaps = require('gulp-sourcemaps');
 var buffer = require('vinyl-buffer');
+var jshint = require('gulp-jshint');
 
 gulp.task('build', function() {
     var app = browserify('./src/js/main.js');
@@ -16,8 +17,14 @@ gulp.task('build', function() {
         .pipe(gulp.dest('./dist'))
 });
 
+gulp.task('lint', function() {
+  return gulp.src('src/**/*.js')
+    .pipe(jshint())
+    .pipe(jshint.reporter('default'));
+});
+
 gulp.task('watch', function() {
     gulp.watch('src/**/*.js', ['build']);
 });
 
-gulp.task('default', ['build']);
+gulp.task('default', ['lint', 'build']);