Add icon for iOS home screen (Springboard)

As of iOS 8 (or possibly 7?) this is also applicable for bookmarks and often-visited sites in safari. Currently this page shows a white safari logo on a grey background. I have the SVG if you want ((me?) to make) modifications to the icon. I have tested this change with `python3 -m http.server`, but not on a real Campfyre instance. Here are some screenshots of how it looks:

![photo 2-11-14 6 56 16 pm](https://cloud.githubusercontent.com/assets/691552/4874439/18fe08ce-6256-11e4-8964-d6f185ef1d5a.png)
![photo 2-11-14 6 56 23 pm](https://cloud.githubusercontent.com/assets/691552/4874440/18fe5d38-6256-11e4-8236-ecfc54b48734.png)
![photo 2-11-14 6 56 33 pm](https://cloud.githubusercontent.com/assets/691552/4874441/19022e22-6256-11e4-8509-981672779533.png)