Put `ruby-shadow` package installation part in `base` cookbook alone.

`ruby-shadow` installation part are unnecessarily put on the several cookbooks.

In order to maintaine these cookbooks easily,
put `ruby-shadow` package installation part in `base` cookbook alone.

This commit refs #85.
Merge pull request #85 from kazu634/id/85

`ruby-shadow` gemのインストールを一箇所に集約する