Require files to pass gofmt on Travis builds

Added a `before_script` to the Travis build which runs `go fmt ./...` on the code, and fails the build immediately if there are any files which are modified. This should mean no more running `gofmt`, as only correctly formatted code (according to the go standards) can pass the build.

Also ran `gofmt` on the `cloudwatch` and `ec2` modules, which fixes some formatting errors.