added default skin css file

tracim/tracim/public/assets/css/dashboard.css

   }
 }
 
-/* start rules that will be overriden by theme builder */
-.textMenuClickedBgColor {
-  background: #beebff;
-}
-.textMenuClickedColor {
-  color: #333;
-}
-.textMenuBgColor-hover {
-  background-color: #e7f4f9;
-}
-.textMenuColor-hover {
-  color: #333;
-}
-/* end rules that will be overriden by theme builder */
-
-
 .sidebarleft__menu__item__link > .fa-bank {
   color: #DDD;
 }

tracim/tracim/public/assets/css/default_skin.css

+/*
+* this file is used to declare default tracim skin before bootstrap.min.css so that the bootstrap.css file generated by tracim_theme
+* can override them withtout adding specificity, just by rules declaration order
+*/
+.textMenuClickedBgColor {
+  background: #beebff;
+}
+.textMenuClickedColor {
+  color: #333;
+}
+.textMenuBgColor-hover {
+  background-color: #e7f4f9;
+}
+.textMenuColor-hover {
+  color: #333;
+}

tracim/tracim/templates/master_authenticated.mak

         <meta name="description" content="">
         <meta name="author" content="">
         <link rel="icon" href="/favicon.ico">
+        <link href="${tg.url('/assets/css/default_skin.css')}" rel="stylesheet">
         <link href="${tg.url('/assets/css/bootstrap.min.css')}" rel="stylesheet">
         <link href="${tg.url('/assets/font-awesome-4.2.0/css/font-awesome.css')}" rel="stylesheet">
         <link href="${tg.url('/assets/select2-4.0.3/css/select2.min.css')}" rel="stylesheet">