title: Nested if is not working in eco template engine
body: <p>I was trying use nested if in eco template. Here is my code </p>
  
  <pre><code>&lt;% for document in @getCollection('posts').toJSON()[@document.page.startIdx...@document.page.endIdx]: %&gt;
  
                      &lt;% if true %&gt;
  
                          &lt;p&gt;  &lt;%=  new Date(document.date.toDateString()).getTime() &lt;= new Date(new Date().toDateString()).getTime() %&gt; &lt;/p&gt;
  
  
                          &lt;div class='row-fluid'&gt;
                              &lt;div class='span12 blogShadow'&gt;
                                  &lt;div class="row-fluid"&gt;
                                      &lt;div class='span12 archiverow'&gt;
                                          &lt;span&gt;(&lt;%= document.date.toDateString() %&gt;) =&gt; &lt;/span&gt;
                                          &lt;span&gt;
                                              &lt;a href="&lt;%= document.url %&gt;"&gt;   &lt;%= document.title %&gt; &lt;/a&gt;
                                          &lt;/span&gt;
                                      &lt;/div&gt;
                                  &lt;/div&gt;
                                  &lt;div class="row-fluid archiverow"&gt;
                                      &lt;% if document.img:%&gt;
                                          &lt;img class="span1" src="&lt;%= document.img %&gt;" width=100 height=100 /&gt;
                                          &lt;span class="span11"&gt;&lt;%= document.description %&gt;&lt;/span&gt;
                                      &lt;% else: %&gt;
                                          &lt;span class="span12"&gt;&lt;%= document.description %&gt;&lt;/span&gt;
                                      &lt;% end %&gt;
                                  &lt;/div&gt;
                              &lt;/div&gt;
                          &lt;/div&gt;
                      &lt;% end %&gt;
                      &lt;br/&gt;
                      &lt;br/&gt;
                  &lt;% end %&gt;
  </code></pre>
  
  <p>if I remove first if with its corresponding end statement things working fine, but if I put that it is giving parsing error with message unexpected dedent.</p>
  
  <p>for the else statement down there </p>
  
  <pre><code>&lt;% else: %&gt;
                                          &lt;span class="span12"&gt;&lt;%= document.description %&gt;&lt;/span&gt;
                                      &lt;% end %&gt;
  </code></pre>
  
  <p>I am new to eco and I don't understand the message. Is this kind of nested if is possible and if not what is the work around for this. </p>
  
  <p>As, I am using docpad and eco I am using as template engine. </p>
  
  <p>Please let me know if any further details is required.</p>