Set baseurl to blank for expected behavior

When cloning this theme, it's expected that Jekyll will serve the site
from the root. "baseurl" must be set to an empty string since the
default is "/", which breaks the absolute URLs defined in the templates.

Fixes #8.
Depend on 'github-pages' to run Jekyll

'github-pages' is a Gem that contains the Gem dependencies used to run
GitHub Pages. By using it to run Jekyll locally, you ensure your site
will build properly when deployed to GitHub Pages.

To run locally with Bundler:

    bundle install
    bundle exec jekyll serve --watch
Merge pull request #9 from ssorallen/blank-baseurl

Set baseurl to blank for expected behavior
Merge pull request #10 from ssorallen/gem-dependencies

Depend on 'github-pages' to run Jekyll