Add missing `.small` styles and docs

Created by: zlatanvasovic

Quick fix to improve .small.

dist/css/bootstrap.css

@@ -692,13 +692,15 @@ blockquote p:last-child {
   margin-bottom: 0;
 }
 
-blockquote small {
+blockquote small,
+blockquote .small {
   display: block;
   line-height: 1.428571429;
   color: #999999;
 }
 
-blockquote small:before {
+blockquote small:before,
+blockquote .small:before {
   content: '\2014 \00A0';
 }
 

less/type.less

@@ -233,7 +233,8 @@ blockquote {
   p:last-child {
     margin-bottom: 0;
   }
-  small {
+  small,
+  .small {
     display: block;
     line-height: @line-height-base;
     color: @blockquote-small-color;

css.html

@@ -871,7 +871,7 @@ base_url: "../"
     <p>Style and content changes for simple variations on a standard <code>&lt;blockquote&gt;</code>.</p>
 
     <h4>Naming a source</h4>
-    <p>Add <code>&lt;small&gt;</code> tag for identifying the source. Wrap the name of the source work in <code>&lt;cite&gt;</code>.</p>
+    <p>Add <code>&lt;small&gt;</code> tag or <code>.small</code> class for identifying the source. Wrap the name of the source work in <code>&lt;cite&gt;</code>.</p>
     <div class="bs-example">
       <blockquote>
         <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer posuere erat a ante.</p>