Do not fall back to author-associated role for blog posts (fixes #18)

[jennifer-richards]

As described in the discussion on ietf-tools#18, the blog post displays should only display a role for an author if it explicitly associated with them. The mechanism for that is a "role override." This pull request removes the template code that fell back to a role associated with the author when there was no role override.

The formatting issue (unwanted separator) is cleaned up by this as well. That was a side effect of a bug in the now-removed code that rendered an empty <li></li> in place of the role, triggering the CSS to display a separator between them.

[meadmaker]

This change looks to meet the request from @rjsparks to remove the fallback to the author-associated role. However, it doesn't do anything about the separator between the person and the role that shows up when there isn't a role displayed. That should be addressed as well.

[jennifer-richards]

It fixes that also - that's what the second paragraph of my description was trying to say.

The CSS puts a separator between <li> elements. In the old code, a bug was causing there to actually be a second entry but it was always an empty string. The unwanted separator was separating the name from that empty <li>.

Now there is no second <li> if there is no role, and the CSS handles that correctly by not showing the separator.

[meadmaker]

Ah, OK.