Remove assets in preparation of Jekyll 2.0 upgrade.
Upgrade to Jekyll 2.0 (resolves #24)

- Update Gemfile
- Remove custom development configuration file (and reference in Procfile)
- Remove assets-related Liquid tag in layout
Move blog posts.
Remove category from post template.
Update post rake task to point to new posts path.
Re-work Jekyll configuration. Update templates with new variables from configuration.
Add skip to content links. Resolves #20
Reorder link elements alphabetically.
Fix typo in configuration.
Remove pygments configuration for the time being.
Use front matter defaults for blog posts. Remove layout setting from posts.