Optimized images in directory

What did I do?
- optimized all png-images with advanced optipng
- optimized all jpg-images with jpegtran (keeing meta-data)
- resized all students/mentors images to width 300px keeing aspect radio using imgaemagick

I tested website - it looks well.

https://www.google-melange.com/gci/task/view/google/gci2014/5238574983151616