Merge pull request #47 from javiercejudo/release-1.2.4

Release 1.2.4
Installs Wraith via gemfile and tweaks config
Merge pull request #48 from javiercejudo/wraith-integration

Installs Wraith via gemfile and tweaks config
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.
Try the anvil strategy to see if it prevents missing config vars
Back to git strategy
Adds new config vars allows failures for some browsers
Removes allow_failures option
Fix Sauce Labs access key
Adds proper Procfile
Refactors deployment strategy
Refactors deployment strategy, again
Refactors deployment strategy, and again
Fixes deployment, probably