add platform notifications to os module #3951

#3951

**EDIT: Ready for review**

Stable but incomplete. This can be safely merged into dev, changes will only occur after an RSS feed has been added as a setting.

### Changes

* Added 2 new library declarations: External google feeds api, Hopscotch tours API
* Under certain conditions, the toolbar build has new js, css, and libraries attached
* Currently, feed items are parsed and loaded into a tour, but there is no counter or "dismiss" logic.

### Screenshots

Testing settings:
![screen shot 2013-10-16 at 2 45 09 pm](https://f.cloud.github.com/assets/228733/1345683/a07a1530-3693-11e3-9812-5a0d2c7b5735.png)

Current appearance:
![screen shot 2013-10-16 at 2 45 19 pm](https://f.cloud.github.com/assets/228733/1345685/acc88470-3693-11e3-9c2c-b5852d4fc858.png)