New grass & leaves textures

Before / after : 

![grass](https://cloud.githubusercontent.com/assets/9149204/4606171/2cdf2d68-5212-11e4-8c83-d80b7d3b38c7.jpg)

![tree](https://cloud.githubusercontent.com/assets/9149204/4675492/e97087d8-55dc-11e4-9ad8-6298f25c1bc9.jpg)