cleaned up sass-lint warnings and elevated them to be errors

Author: travi

.sass-lint.yml

@@ -1,3 +1,8 @@
 rules:
   force-element-nesting: 2
-  force-pseudo-nesting: 2
+  force-pseudo-nesting: 2
+  no-trailing-whitespace: 2
+  empty-line-between-blocks: 2
+  nesting-depth:
+    - 2
+    - max-depth: 3

src/theme/nav/_navbar.scss

@@ -12,7 +12,7 @@
 
     a {
       @extend %h1;
-        
+
       &:visited,
       &:active {
         @extend %h1;