Added updated document icons

For the Mac version. Yosemite style. E.g.:

![icon_16x16](https://cloud.githubusercontent.com/assets/3859425/5239117/c01edeb4-78d4-11e4-9b72-7e15adec1032.png)
![icon_16x16 2x](https://cloud.githubusercontent.com/assets/3859425/5239122/c030ab76-78d4-11e4-858b-812a7476ae5f.png)
![icon_32x32 2x](https://cloud.githubusercontent.com/assets/3859425/5239118/c0204ea2-78d4-11e4-848b-125fc9f50d6a.png)
![icon_128x128](https://cloud.githubusercontent.com/assets/3859425/5239121/c0218696-78d4-11e4-9ffb-0bbd21e34e4d.png)
![icon_128x128 2x](https://cloud.githubusercontent.com/assets/3859425/5239120/c02153f6-78d4-11e4-9b1d-8e5e0ca3ad14.png)
![icon_256x256 2x](https://cloud.githubusercontent.com/assets/3859425/5239119/c021208e-78d4-11e4-911b-70de2301db4a.png)
![icon_512x512 2x](https://cloud.githubusercontent.com/assets/3859425/5239123/c03aed0c-78d4-11e4-8bfe-5b61a60215db.png)