For the record Travis is not the only option in town, you can use [wercker](http://wercker.com/) or [Bitrise](http://www.bitrise.io/) too. There's even a tutorial on [how to publish middleman based sites/blogs](http://devcenter.bitrise.io/tutorials/middleman-project.html) on Bitrise - though Bitrise is currently an iOS CI/CD focused service but generally speaking it's a PaaS with OS X virtual machines.