fix composer

Uses

    "cakephp/plugin-installer": "*"

Fixes composer error:
```
  Problem 1
    - Installation request for gourmet/twitter_bootstrap dev-master -> satisfiab
le by gourmet/twitter_bootstrap[dev-master].
    - gourmet/twitter_bootstrap dev-master requires cakephp/plugin-installer dev
-master -> no matching package found.
```