ci-stackato

Fix errors that are appearing when staging the stackato instance:
```bash
staging:          - Installing wp-cli/wp-cli (v0.12.0)
staging:            Cloning a9b9c2d37ae80c927d378cda2ede2442cbeafc0c
Failed to stage application:
 staging plugin exited with non-zero exit code.
```
eg:
http://ci.labs.cityindex.com:8080/job/wordpress-development-flow(pull%20requests)/93/console