chore(install.sh): update deisctl version to 0.13.0-dev

Until Deis has a stable release, we probably want everyone getting the latest version of `deisctl` through our one-line install script.

Double-check the URLs it should generate:
https://s3-us-west-2.amazonaws.com/opdemand/deisctl-0.13.0-dev-darwin-amd64.run
https://s3-us-west-2.amazonaws.com/opdemand/deisctl-0.13.0-dev-linux-amd64.run