Conf link on landing page

[plaindocs]

When there is a conference on we sometimes manually link to the current conference.

We could do some fairly janky iterating over config files that match the current year, do some simple logic based on flags and date fields, and put it up automatically.

CC @ddbeck @mxsasha

[ericholscher]

I went ahead and moved the confs to the top of the front page:

Baby steps..?