Add Github's github-pages gem

Sets the necessary dependencies and versions required for publishing to
Github Pages using [Jekyll](http://jekyllrb.com/).

Note the inclusion of the JSON gem, which is also required but is not
pulled in by the github-pages gem.
Remove default welcome post
[about] Add info about me
[config] Set site name and description
[config] Set some sensible configuration settings
[config] Set my name, email address and the URL
[post] First post explaining this blog
[layout] Set my name and email for copyright
[layout] Set my Google Analytics ID
[layout] Set disqus username
[layout] Add author description and Gravatar