Add "lint" gulp command with sass linting.

gulpfile.js/tasks/lint.js

@@ -0,0 +1,26 @@
+var gulp = require('gulp');
+
+var sassLint = require('gulp-sass-lint');
+var pump = require('pump');
+
+var watchConfig = require('../config.js').watchConfig;
+
+
+gulp.task('lint', ['lint:styles']);
+
+gulp.task('lint:styles', function(cb) {
+    pump([
+        gulp.src(watchConfig.stylesGlob),
+        sassLint({
+            rules: {
+                'declarations-before-nesting': 1,
+                'indentation': [ 1, { 'size': 4 } ],
+                'no-ids': 0,
+                'no-vendor-prefixes': 2,
+                'property-sort-order': 0
+            }
+        }),
+        sassLint.format(),
+        sassLint.failOnError()
+    ], cb);
+});

package.json

@@ -10,6 +10,7 @@
     "gulp-csso": "^3.0.0",
     "gulp-sass": "^3.1.0",
     "gulp-sass-glob": "^1.0.8",
+    "gulp-sass-lint": "^1.3.2",
     "gulp-uglify": "^3.0.0",
     "jquery": "^3.2.1",
     "moment": "^2.18.1",