Fix SASS syntax err, build theme.css for #432

Author: benjaoming

sphinx_rtd_theme/static/css/theme.css

@@ -429,10 +429,10 @@ footer
     vertical-align: top
 
 +media($desktop-wider)
-   .wy-nav-content-wrap
-     background: rgba(0,0,0,.05)
+  .wy-nav-content-wrap
+    background: rgba(0,0,0,.05)
   .wy-nav-content
-     background: $section-background-color
+    background: $section-background-color
 
 @media print
   .rst-versions, footer, .wy-nav-side