Update validator to 1.5.1

Author: smelukov

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "csstree-validator",
-  "version": "0.6.0",
+  "version": "0.7.0",
   "description": "Validate CSS according to W3C specs and browser implementations",
   "main": "lib/index.js",
   "repository": "csstree/atom-plugin",
@@ -26,7 +26,7 @@
   "dependencies": {
     "atom-linter": "^10.0.0",
     "atom-package-deps": "^4.0.1",
-    "csstree-validator": "~1.4.0"
+    "csstree-validator": "~1.5.1"
   },
   "package-deps": [
     "linter"