fix: add transparent outline color

Some browser styles add an outline to focused elements, which makes for a few strange interactions when you click the animations you want to see in action.

![outline-color-chrome-2](https://cloud.githubusercontent.com/assets/887163/3384403/966ea060-fc59-11e3-8c78-9821f8af8bdc.png)

If you have a finicky graphics card like me, this is specially visible

![outline-color-chrome-1](https://cloud.githubusercontent.com/assets/887163/3384465/b80594bc-fc5a-11e3-8847-f4feb8dce454.png)

I don't know if the outline's intended, but this PR tries to minimize that by setting the ```outline-color``` to transparent.

Thanks!