Prepare for publishing.

* Move `bower install` into `prepublish`.  This prevents consumers of the new published `ember-data` package from having `bower` installed globally. Also, nothing changes as far as setup requirements: running `npm install` in the root of the repo runs the `prepublish` script.
* Only publish the specific files that we want (leaves ability in the future to publish other types of things).
Yup, our options parsing doesn't care if it has an equals or not, both are perfectly valid.