Upload assets to S3 and serve from CloudFront in live
Set ENV back to dev in .env.dist
Add vary accept-encoding header to JS and CSS assets
Adds external assets to appcache
Move rev-manifest loading inside manifest task
Adds cloudfront URL to travis as a global config var
Merge pull request #49 from javiercejudo/cloudfront-assets

Upload assets to S3 and serve from CloudFront in live. Closes #41.