Topcoat issue 422 -- switch background hidden

Problem with z-index. Fix by adding z-index: 1; to base component
updated topcoat-switch to pass the tests

![screenshot from 2013-11-20 00 54 49](https://f.cloud.github.com/assets/810040/1577643/a0f2e8bc-516d-11e3-8c16-410ce0475f30.png)