Revamp Tumblr theme

This is actually live right now: http://news.teslaworks.net/

Improvements include:
- Matching nav bar (masthead)
- Better (IMO) title link styling
- Better (IMO) date link styling
- Narrower page
- "Polaroid" image styling
- Updates automatically from main site CSS (for general style)

Closes #85 
Closes #90 
Closes #108