Update Ruby dependencies in Gemfile.
Change `layout: none` to layout: null` in sitemap.xml YAML front matter to no longer get warning when building the site.
Simplify .editorconfig by setting the `indent_size` to 2 for everything but Markdown files.
Add MIT license to project.
Add .ruby-version to project with ruby-2.1.2.
Update _config.yml by removing some unnecessary defaults to simplify things a bit.