Syncing Blog content and assets

Ready for merge.
So, it turns out that this `_config` template *is* used, but for staging and production. See: https://github.com/rackerlabs/developer.rackspace.com/blob/dev/build_site.sh#L40-L42

I know that's a little weird. It was the best way I could work out so that `vagrant up, `script/deploy`, and just jamming `./build_site.sh` would all Just Work fresh off the clone.

How about this, instead:

```
# THIS FILE IS NOT USED BY VAGRANT. It's used by Jenkins to build the production and
# staging sites.
#
# If you want to modify the Jekyll configuration used by everyone's Vagrant machine, edit:
#   deploy/roles/dev/files/_config.yml
# To make those changes permanent, copy them here.
```