bugfix for permalink for subdirectories

package.json

@@ -1,6 +1,6 @@
 {
     "name": "@site-o-mat/core",
-    "version": "0.5.2",
+    "version": "0.5.3",
     "build": "webpack",
     "author": "Björn Hase <me@herr-hase.wtf>",
     "main": "index.js",

src/factories/page.js

@@ -61,6 +61,7 @@ class Page {
         if (fs.existsSync(configStore.get('source') + this._permalink) && this._slug) {
             this._dirPath += '/' + this._slug
             this._filename = 'index'
+            this._permalink += '/'
         }
 
         this._filename += '.' + this._fields.extensions