Merge pull request #71 from bvssvni/master

Updated Cargo.lock
Port to gfx-rs
Merge pull request #70 from cmr/gfx

Port to gfx-rs
fps_counter: rolling frame counter for accurate FPS.
Remove any FPS caps to allow accurate comparisons.
Move buffer building out of the event loop.
Merge pull request #74 from eddyb/fps-counter

FPS counter.
Update to latest piston and gfx-rs