* improve avatar UI.

src/less/controls/avatar.less

@@ -11,10 +11,11 @@
   width: @avatar-size;
   height: @avatar-size;
   line-height: @avatar-size;
-  vertical-align: middle;
   text-align: center;
   background-position: center;
   background-size: cover;
+  border-radius: @border-radius-base;
+  position: relative;
 
   img {
     display: block;
@@ -51,3 +52,7 @@
 
   > .icon {font-size: (@avatar-size-xl/2)}
 }
+
+.avatar-circle {
+  border-radius: 50%;
+}