Build inital static source for site.

The site will be built using a static site generator
in Ruby - Middleman. This commit includes the init
files that Middleman creates with minor changes.

- Add Gemfile for dependency management.
- Add Middleman gem dependency.
- Add Slim gem dependency.
- Use config file from Middleman init.
- Setup initial views (layout and index).
- Use Slim template engine in place of Haml.