Realiza pequenas modificações no cabeçalho das vignettes

vignettes/_before_body.html

 <style type="text/css">
 div.header {
     margin-top: 20px;
-    line-height: 20%;
+    border-bottom: 1px solid #BCBCBC;
 }
 table.header {
     margin-top: 10px;
 }
 </style>
 
-<table class="header" width="100%">
+<table class="header" width="100%" align="center">
   <tr>
-    <td align="left" valign="bottom" width="100px">
-      <img src="img/MRDCr_logo.png" width="80px" />
+    <td align="left" valign="bottom" width="90px">
+      <img src="img/MRDCr_logo.png" width="100%" />
     </td>
     <td align="left" valign="top">
       <div class="header">
-        <h4>
+        <h4 style="font-size: 20px; margin: 10px">
           Modelos de Regressão para Dados de Contagem com o R
         </h4>
-        <em><a href="https://github.com/leg-ufpr/MRDCr">
-            github.com/leg-ufpr/MRDCr
-        </a></em>
+        <h5 style="margin: 0px 0px 10px 10px">
+          <a href="https://github.com/leg-ufpr/MRDCr">
+          <code>github.com/leg-ufpr/MRDCr</code>
+          </a>
+        </h5>
       </div>
     </td>
   </tr>