App icon - close #87

[jeremiak]

This PR has 2 consequences:

• when a user adds bestnest as a home screen bookmark on ios they will get a nice app icon for their home screen
• when a user opens the resulting bookmark, the safari user interface components will be hidden to make it appear even more like a native application

The changes required for this are pretty simple:

1. new grunt task img-dev to make sure images are available after the build
2. <meta> tags added to the root index.html to tell ios where to find the images

[junosuarez]

merging for demo purposes but we should still fix the gulp task