Add Amazon S3 deploy option to rake tasks

- Jekyll: a static-site generator
- Amazon S3: allows easy static-site web hosting
- Octopress + S3 Deploy Task: An awesome way to deploy an awesome site to an awesome hosting platform

There are (small) data transfer fees which hopefully anyone using S3 is aware of, but I'll provide the [pricing reference](http://aws.amazon.com/s3/#pricing) to be helpful.

Was #944; rebased and reworked for branch 2.1.