Make block rendering more developer friendly

[mplatts]

normal hamlbars:

{{#if messages}}<ul class='alert'>
  {{#each messages}}<li>{{{this}}}</li>{{/each}}
</ul>{{/if}}

hamlbars with my modifications:

{{#if messages}}
  <ul class='alert'>
    {{#each messages}}
      <li>{{{this}}}</li>
    {{/each}}
  </ul>
{{/if}}

[sethjeffery]

👍 I also recommend making a PR from this fork into the main hamlbars repo.