Enable using dotted access notation in a section

[fotoetienne]

Fails (prints nothing):
{{#photos}} {{thumb.src}} {{/photos}}

Works (prints photo's thumb's src):
{{#photos}} {{#thumb}}{{src}}{{/thumb}} {{/photos}}

First example should work same as second one, but it fails.

Failing test case:

(deftest test-render-tag-with-dotted-name-like-section--inside-another-section
  (is (= "photo thumb" (render "{{#photos}}{{src}} {{thumb.src}}{{/photos}}"
                               {:photos [{:src "photo" :thumb {:src "thumb"}}]}))))

See also:
fhd#32
fhd#44