Simple Redirects

Setup simple "301 Moved Permanently" redirects through the config file:

``` yaml
redirects:
  index.php: /
  about.php: about.html
  promo.mp4: http://www.youtube.com/watch?v=dQw4w9WgXcQ
```

See #48 for a discussion on the feature. I opted for the third approach because it was the easiest to implement. Looking at the AWS Ruby SDK I couldn't find an easy way to generalize managing metadata.