breaking changes: widget 寫法更改/可添加非sticky區域widget

feat: 升級facebook comment js 到 v10
fix: 修復當內容過少時， footer 沒有底部靠攏的bug
improvement: 404頁面不再顯示 rightside

source/css/_layout/head.styl

@@ -9,7 +9,7 @@
 
   // index
   &.full_page
-    height: $index_top_img_height
+    min-height: $index_top_img_height
     background-attachment: fixed
 
     #site-info
@@ -70,7 +70,7 @@
 
   // page
   &.not-home-page
-    height: 20rem
+    min-height: 20rem
 
     +maxWidth768()
       height: 14rem
@@ -86,7 +86,7 @@
 
   // post
   &.post-bg
-    height: 20rem
+    min-height: 20rem
 
     +maxWidth768()
       height: 18rem
@@ -118,7 +118,7 @@
 
   &.not-top-img
     margin-bottom: .5rem
-    height: 60px
+    min-height: 60px
     background: 0
 
     #nav