feat(social): improve social links (#254)

* replace forkawesome and iconfont with simple icons
* add more configs for social

assets/css/_partial/_header.scss

@@ -2,6 +2,7 @@ header {
   width: 100%;
   z-index: 150;
   background-color: $header-background-color;
+  @include box-shadow(0px 1px 4px rgba(0, 0, 0, .1));
 
   .dark & {
     background-color: $header-background-color-dark;

assets/css/_partial/_icon.scss

@@ -0,0 +1,10 @@
+svg.icon {
+  display: inline-block;
+  width: 1.25em;
+  height: 1em;
+  text-align: center;
+
+  path {
+    fill: currentColor;
+  }
+}

assets/css/_partial/_single/_footer.scss

@@ -39,6 +39,12 @@
 
         @include link(false, false);
       }
+
+      .post-info-share {
+        a * {
+          vertical-align: text-bottom;
+        }
+      }
     }
   }