Changes site from Github Pages to S3

* Removes compiled content from repo
* Sets up Gulp to build out and deploy site
  * build dir changed to ./build
  * adds gulp dependencies
  * creates gulp tasks to clean out build dir, compile and minify css and js, run Wintersmith, and deploy the resulting build/ to s3 bucket
  * all non-compiled content and images moved to contents/ to be copied by Wintersmith
* build/, AWS credentials, and upload cache added to gitignore
Removes Grunt in favor of Gulp

* Kills Gruntfile; removes unnecessary modules from package.json