Using h2 and h4 in gerrit_review_queue.html

Changing <h4> for <h2>, and <h6> for <h4>, in order to increase fonts and use more normal levels of headers. The idea is to change the other pages when we are happy with this one.
Merge pull request #48 from quimgil/patch-10

Using h2 and h4 in gerrit_review_queue.html