Set up baseurl support for GitHub Pages

This modification allows Lanyon to adapt if hosted on a GitHub Page without a
custom domain. Please refer to Jekyll's guide
http://jekyllrb.com/docs/github-pages/
for details on how it works. Basically, if your site is on a subdomain, set
baseurl in _config.yml to the subdomain. Do not include ending slashes, but do
include leading slashes. If not on a subdomain (eg you set a custom domain)
then leave baseurl as it is, ie the empty string.
Change @media queries from rem to px

Fixes an issue in some browsers where @media queries involving rem are not
calculated properly, resulting in UI quirks (eg pagination buttons stacked
vertically instead of side-by-side).

This is probably not a good change overall, but in one of my environments I
use Midori, which exhibits this problem, so I had to fix it. To see if your
browser has it as well, check http://fvsch.com/code/bugs/rem-mediaquery/
Add post list

Adds a simple post list page to Lanyon. The list uses the `page` layout, so it
will appear in the sidebar. A button on the index, in between Older and Newer,
is also available to jump to the post list.
Change fonts to Liberation Sans and Inconsolata
Change date format from "01 Jan 2014" to "Jan 1 2014"
Reverse sidebar from left to right