Add beginning of nav bar

Add names of the items that I would like to have but I haven't got yet.
Add more styling to the posts

Changes:
- Add some headers to help with visual hierarchy
- Format footer of post excerpt to better show author, tags and date
  published.
- Add a read more link to the rest of the post.
Add DS_Store to git ignore

This is an OSX generated file. Ignore it.
Add skeleton css 2.0 to project

Skeleton css found here: http://getskeleton.com/. Acts as a nice
boilerplate for all my css needs.
Add link to screen.css and style content

Changes:
- Add grid styling to main content
- Add a link to screen css for styling.
Add blog title and description to page