Remove std::vec::Vec import
Remove std::vec::Vec import

std::vec::Vec is now in the prelude

bjz/glfw-rs,bvssvni/glfw-rs,PistonDevelopers/glfw-rs,derekdreery/glfw-rs,mneumann/glfw-rs,nstoddard/glfw-rs,derekdreery/glfw-rs,tomaka/glfw-rs,servo/glfw-rs